super.c

  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 inode *inode = folio->mapping->host;
105	loff_t offset, size;
106	unsigned long fillsize, pos;
107	void *buf;
108	int ret;
109
110	buf = kmap_local_folio(folio, 0);
111
112	offset = folio_pos(folio);
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			fillsize = 0;
125			ret = -EIO;
126		}
127	}
128
129	buf = folio_zero_tail(folio, fillsize, buf + fillsize);
130	kunmap_local(buf);
131	folio_end_read(folio, ret == 0);
132	return ret;
133}
134
135static const struct address_space_operations romfs_aops = {
136	.read_folio	= romfs_read_folio
137};
138
139/*
140 * read the entries from a directory
141 */
142static int romfs_readdir(struct file *file, struct dir_context *ctx)
143{
144	struct inode *i = file_inode(file);
145	struct romfs_inode ri;
146	unsigned long offset, maxoff;
147	int j, ino, nextfh;
148	char fsname[ROMFS_MAXFN];	/* XXX dynamic? */
149	int ret;
150
151	maxoff = romfs_maxsize(i->i_sb);
152
153	offset = ctx->pos;
154	if (!offset) {
155		offset = i->i_ino & ROMFH_MASK;
156		ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
157		if (ret < 0)
158			goto out;
159		offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
160	}
161
162	/* Not really failsafe, but we are read-only... */
163	for (;;) {
164		if (!offset || offset >= maxoff) {
165			offset = maxoff;
166			ctx->pos = offset;
167			goto out;
168		}
169		ctx->pos = offset;
170
171		/* Fetch inode info */
172		ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
173		if (ret < 0)
174			goto out;
175
176		j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
177				      sizeof(fsname) - 1);
178		if (j < 0)
179			goto out;
180
181		ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
182		if (ret < 0)
183			goto out;
184		fsname[j] = '\0';
185
186		ino = offset;
187		nextfh = be32_to_cpu(ri.next);
188		if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
189			ino = be32_to_cpu(ri.spec);
190		if (!dir_emit(ctx, fsname, j, ino,
191			    romfs_dtype_table[nextfh & ROMFH_TYPE]))
192			goto out;
193
194		offset = nextfh & ROMFH_MASK;
195	}
196out:
197	return 0;
198}
199
200/*
201 * look up an entry in a directory
202 */
203static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
204				   unsigned int flags)
205{
206	unsigned long offset, maxoff;
207	struct inode *inode = NULL;
208	struct romfs_inode ri;
209	const char *name;		/* got from dentry */
210	int len, ret;
211
212	offset = dir->i_ino & ROMFH_MASK;
213	ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE);
214	if (ret < 0)
215		goto error;
216
217	/* search all the file entries in the list starting from the one
218	 * pointed to by the directory's special data */
219	maxoff = romfs_maxsize(dir->i_sb);
220	offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
221
222	name = dentry->d_name.name;
223	len = dentry->d_name.len;
224
225	for (;;) {
226		if (!offset || offset >= maxoff)
227			break;
228
229		ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));
230		if (ret < 0)
231			goto error;
232
233		/* try to match the first 16 bytes of name */
234		ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,
235				       len);
236		if (ret < 0)
237			goto error;
238		if (ret == 1) {
239			/* Hard link handling */
240			if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
241				offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
242			inode = romfs_iget(dir->i_sb, offset);
243			break;
244		}
245
246		/* next entry */
247		offset = be32_to_cpu(ri.next) & ROMFH_MASK;
248	}
249
250	return d_splice_alias(inode, dentry);
251error:
252	return ERR_PTR(ret);
253}
254
255static const struct file_operations romfs_dir_operations = {
256	.read		= generic_read_dir,
257	.iterate_shared	= romfs_readdir,
258	.llseek		= generic_file_llseek,
259};
260
261static const struct inode_operations romfs_dir_inode_operations = {
262	.lookup		= romfs_lookup,
263};
264
265/*
266 * get a romfs inode based on its position in the image (which doubles as the
267 * inode number)
268 */
269static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
270{
271	struct romfs_inode_info *inode;
272	struct romfs_inode ri;
273	struct inode *i;
274	unsigned long nlen;
275	unsigned nextfh;
276	int ret;
277	umode_t mode;
278
279	/* we might have to traverse a chain of "hard link" file entries to get
280	 * to the actual file */
281	for (;;) {
282		ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
283		if (ret < 0)
284			goto error;
285
286		/* XXX: do romfs_checksum here too (with name) */
287
288		nextfh = be32_to_cpu(ri.next);
289		if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
290			break;
291
292		pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
293	}
294
295	/* determine the length of the filename */
296	nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
297	if (IS_ERR_VALUE(nlen))
298		goto eio;
299
300	/* get an inode for this image position */
301	i = iget_locked(sb, pos);
302	if (!i)
303		return ERR_PTR(-ENOMEM);
304
305	if (!(inode_state_read_once(i) & I_NEW))
306		return i;
307
308	/* precalculate the data offset */
309	inode = ROMFS_I(i);
310	inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
311	inode->i_dataoffset = pos + inode->i_metasize;
312
313	set_nlink(i, 1);		/* Hard to decide.. */
314	i->i_size = be32_to_cpu(ri.size);
315	inode_set_mtime_to_ts(i,
316			      inode_set_atime_to_ts(i, inode_set_ctime(i, 0, 0)));
317
318	/* set up mode and ops */
319	mode = romfs_modemap[nextfh & ROMFH_TYPE];
320
321	switch (nextfh & ROMFH_TYPE) {
322	case ROMFH_DIR:
323		i->i_size = ROMFS_I(i)->i_metasize;
324		i->i_op = &romfs_dir_inode_operations;
325		i->i_fop = &romfs_dir_operations;
326		if (nextfh & ROMFH_EXEC)
327			mode |= S_IXUGO;
328		break;
329	case ROMFH_REG:
330		i->i_fop = &romfs_ro_fops;
331		i->i_data.a_ops = &romfs_aops;
332		if (nextfh & ROMFH_EXEC)
333			mode |= S_IXUGO;
334		break;
335	case ROMFH_SYM:
336		i->i_op = &page_symlink_inode_operations;
337		inode_nohighmem(i);
338		i->i_data.a_ops = &romfs_aops;
339		mode |= S_IRWXUGO;
340		break;
341	default:
342		/* depending on MBZ for sock/fifos */
343		nextfh = be32_to_cpu(ri.spec);
344		init_special_inode(i, mode, MKDEV(nextfh >> 16,
345						  nextfh & 0xffff));
346		break;
347	}
348
349	i->i_mode = mode;
350	i->i_blocks = (i->i_size + 511) >> 9;
351
352	unlock_new_inode(i);
353	return i;
354
355eio:
356	ret = -EIO;
357error:
358	pr_err("read error for inode 0x%lx\n", pos);
359	return ERR_PTR(ret);
360}
361
362/*
363 * allocate a new inode
364 */
365static struct inode *romfs_alloc_inode(struct super_block *sb)
366{
367	struct romfs_inode_info *inode;
368
369	inode = alloc_inode_sb(sb, romfs_inode_cachep, GFP_KERNEL);
370	return inode ? &inode->vfs_inode : NULL;
371}
372
373/*
374 * return a spent inode to the slab cache
375 */
376static void romfs_free_inode(struct inode *inode)
377{
378	kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
379}
380
381/*
382 * get filesystem statistics
383 */
384static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
385{
386	struct super_block *sb = dentry->d_sb;
387	u64 id = 0;
388
389	/* When calling huge_encode_dev(),
390	 * use sb->s_bdev->bd_dev when,
391	 *   - CONFIG_ROMFS_ON_BLOCK defined
392	 * use sb->s_dev when,
393	 *   - CONFIG_ROMFS_ON_BLOCK undefined and
394	 *   - CONFIG_ROMFS_ON_MTD defined
395	 * leave id as 0 when,
396	 *   - CONFIG_ROMFS_ON_BLOCK undefined and
397	 *   - CONFIG_ROMFS_ON_MTD undefined
398	 */
399	if (sb->s_bdev)
400		id = huge_encode_dev(sb->s_bdev->bd_dev);
401	else if (sb->s_dev)
402		id = huge_encode_dev(sb->s_dev);
403
404	buf->f_type = ROMFS_MAGIC;
405	buf->f_namelen = ROMFS_MAXFN;
406	buf->f_bsize = ROMBSIZE;
407	buf->f_bfree = buf->f_bavail = buf->f_ffree;
408	buf->f_blocks =
409		(romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;
410	buf->f_fsid = u64_to_fsid(id);
411	return 0;
412}
413
414/*
415 * remounting must involve read-only
416 */
417static int romfs_reconfigure(struct fs_context *fc)
418{
419	sync_filesystem(fc->root->d_sb);
420	fc->sb_flags |= SB_RDONLY;
421	return 0;
422}
423
424static const struct super_operations romfs_super_ops = {
425	.alloc_inode	= romfs_alloc_inode,
426	.free_inode	= romfs_free_inode,
427	.statfs		= romfs_statfs,
428};
429
430/*
431 * checksum check on part of a romfs filesystem
432 */
433static __u32 romfs_checksum(const void *data, int size)
434{
435	const __be32 *ptr = data;
436	__u32 sum;
437
438	sum = 0;
439	size >>= 2;
440	while (size > 0) {
441		sum += be32_to_cpu(*ptr++);
442		size--;
443	}
444	return sum;
445}
446
447/*
448 * fill in the superblock
449 */
450static int romfs_fill_super(struct super_block *sb, struct fs_context *fc)
451{
452	struct romfs_super_block *rsb;
453	struct inode *root;
454	unsigned long pos, img_size;
455	const char *storage;
456	size_t len;
457	int ret;
458
459#ifdef CONFIG_BLOCK
460	if (!sb->s_mtd) {
461		if (!sb_set_blocksize(sb, ROMBSIZE)) {
462			errorf(fc, "romfs: unable to set blocksize\n");
463			return -EINVAL;
464		}
465	} else {
466		sb->s_blocksize = ROMBSIZE;
467		sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
468	}
469#endif
470
471	sb->s_maxbytes = 0xFFFFFFFF;
472	sb->s_magic = ROMFS_MAGIC;
473	sb->s_flags |= SB_RDONLY | SB_NOATIME;
474	sb->s_time_min = 0;
475	sb->s_time_max = 0;
476	sb->s_op = &romfs_super_ops;
477
478#ifdef CONFIG_ROMFS_ON_MTD
479	/* Use same dev ID from the underlying mtdblock device */
480	if (sb->s_mtd)
481		sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index);
482#endif
483	/* read the image superblock and check it */
484	rsb = kmalloc(512, GFP_KERNEL);
485	if (!rsb)
486		return -ENOMEM;
487
488	sb->s_fs_info = (void *) 512;
489	ret = romfs_dev_read(sb, 0, rsb, 512);
490	if (ret < 0)
491		goto error_rsb;
492
493	img_size = be32_to_cpu(rsb->size);
494
495	if (sb->s_mtd && img_size > sb->s_mtd->size)
496		goto error_rsb_inval;
497
498	sb->s_fs_info = (void *) img_size;
499
500	if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
501	    img_size < ROMFH_SIZE) {
502		if (!(fc->sb_flags & SB_SILENT))
503			errorf(fc, "VFS: Can't find a romfs filesystem on dev %s.\n",
504			       sb->s_id);
505		goto error_rsb_inval;
506	}
507
508	if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
509		pr_err("bad initial checksum on dev %s.\n", sb->s_id);
510		goto error_rsb_inval;
511	}
512
513	storage = sb->s_mtd ? "MTD" : "the block layer";
514
515	len = strnlen(rsb->name, ROMFS_MAXFN);
516	if (!(fc->sb_flags & SB_SILENT))
517		pr_notice("Mounting image '%*.*s' through %s\n",
518			  (unsigned) len, (unsigned) len, rsb->name, storage);
519
520	kfree(rsb);
521	rsb = NULL;
522
523	/* find the root directory */
524	pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
525
526	root = romfs_iget(sb, pos);
527	if (IS_ERR(root))
528		return PTR_ERR(root);
529
530	sb->s_root = d_make_root(root);
531	if (!sb->s_root)
532		return -ENOMEM;
533
534	return 0;
535
536error_rsb_inval:
537	ret = -EINVAL;
538error_rsb:
539	kfree(rsb);
540	return ret;
541}
542
543/*
544 * get a superblock for mounting
545 */
546static int romfs_get_tree(struct fs_context *fc)
547{
548	int ret = -EINVAL;
549
550#ifdef CONFIG_ROMFS_ON_MTD
551	ret = get_tree_mtd(fc, romfs_fill_super);
552#endif
553#ifdef CONFIG_ROMFS_ON_BLOCK
554	if (ret == -EINVAL)
555		ret = get_tree_bdev(fc, romfs_fill_super);
556#endif
557	return ret;
558}
559
560static const struct fs_context_operations romfs_context_ops = {
561	.get_tree	= romfs_get_tree,
562	.reconfigure	= romfs_reconfigure,
563};
564
565/*
566 * Set up the filesystem mount context.
567 */
568static int romfs_init_fs_context(struct fs_context *fc)
569{
570	fc->ops = &romfs_context_ops;
571	return 0;
572}
573
574/*
575 * destroy a romfs superblock in the appropriate manner
576 */
577static void romfs_kill_sb(struct super_block *sb)
578{
579	generic_shutdown_super(sb);
580
581#ifdef CONFIG_ROMFS_ON_MTD
582	if (sb->s_mtd) {
583		put_mtd_device(sb->s_mtd);
584		sb->s_mtd = NULL;
585	}
586#endif
587#ifdef CONFIG_ROMFS_ON_BLOCK
588	if (sb->s_bdev) {
589		sync_blockdev(sb->s_bdev);
590		bdev_fput(sb->s_bdev_file);
591	}
592#endif
593}
594
595static struct file_system_type romfs_fs_type = {
596	.owner		= THIS_MODULE,
597	.name		= "romfs",
598	.init_fs_context = romfs_init_fs_context,
599	.kill_sb	= romfs_kill_sb,
600	.fs_flags	= FS_REQUIRES_DEV,
601};
602MODULE_ALIAS_FS("romfs");
603
604/*
605 * inode storage initialiser
606 */
607static void romfs_i_init_once(void *_inode)
608{
609	struct romfs_inode_info *inode = _inode;
610
611	inode_init_once(&inode->vfs_inode);
612}
613
614/*
615 * romfs module initialisation
616 */
617static int __init init_romfs_fs(void)
618{
619	int ret;
620
621	pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n");
622
623	romfs_inode_cachep =
624		kmem_cache_create("romfs_i",
625				  sizeof(struct romfs_inode_info), 0,
626				  SLAB_RECLAIM_ACCOUNT | SLAB_ACCOUNT,
627				  romfs_i_init_once);
628
629	if (!romfs_inode_cachep) {
630		pr_err("Failed to initialise inode cache\n");
631		return -ENOMEM;
632	}
633	ret = register_filesystem(&romfs_fs_type);
634	if (ret) {
635		pr_err("Failed to register filesystem\n");
636		goto error_register;
637	}
638	return 0;
639
640error_register:
641	kmem_cache_destroy(romfs_inode_cachep);
642	return ret;
643}
644
645/*
646 * romfs module removal
647 */
648static void __exit exit_romfs_fs(void)
649{
650	unregister_filesystem(&romfs_fs_type);
651	/*
652	 * Make sure all delayed rcu free inodes are flushed before we
653	 * destroy cache.
654	 */
655	rcu_barrier();
656	kmem_cache_destroy(romfs_inode_cachep);
657}
658
659module_init(init_romfs_fs);
660module_exit(exit_romfs_fs);
661
662MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
663MODULE_AUTHOR("Red Hat, Inc.");
664MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */