xref: /openbmc/linux/fs/romfs/super.c (revision b34e08d5)
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 
77 static struct kmem_cache *romfs_inode_cachep;
78 
79 static 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 
90 static 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 
94 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos);
95 
96 /*
97  * read a page worth of data from the image
98  */
99 static 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 
141 static const struct address_space_operations romfs_aops = {
142 	.readpage	= romfs_readpage
143 };
144 
145 /*
146  * read the entries from a directory
147  */
148 static int romfs_readdir(struct file *file, struct dir_context *ctx)
149 {
150 	struct inode *i = file_inode(file);
151 	struct romfs_inode ri;
152 	unsigned long offset, maxoff;
153 	int j, ino, nextfh;
154 	char fsname[ROMFS_MAXFN];	/* XXX dynamic? */
155 	int ret;
156 
157 	maxoff = romfs_maxsize(i->i_sb);
158 
159 	offset = ctx->pos;
160 	if (!offset) {
161 		offset = i->i_ino & ROMFH_MASK;
162 		ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
163 		if (ret < 0)
164 			goto out;
165 		offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
166 	}
167 
168 	/* Not really failsafe, but we are read-only... */
169 	for (;;) {
170 		if (!offset || offset >= maxoff) {
171 			offset = maxoff;
172 			ctx->pos = offset;
173 			goto out;
174 		}
175 		ctx->pos = offset;
176 
177 		/* Fetch inode info */
178 		ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
179 		if (ret < 0)
180 			goto out;
181 
182 		j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
183 				      sizeof(fsname) - 1);
184 		if (j < 0)
185 			goto out;
186 
187 		ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
188 		if (ret < 0)
189 			goto out;
190 		fsname[j] = '\0';
191 
192 		ino = offset;
193 		nextfh = be32_to_cpu(ri.next);
194 		if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
195 			ino = be32_to_cpu(ri.spec);
196 		if (!dir_emit(ctx, fsname, j, ino,
197 			    romfs_dtype_table[nextfh & ROMFH_TYPE]))
198 			goto out;
199 
200 		offset = nextfh & ROMFH_MASK;
201 	}
202 out:
203 	return 0;
204 }
205 
206 /*
207  * look up an entry in a directory
208  */
209 static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
210 				   unsigned int flags)
211 {
212 	unsigned long offset, maxoff;
213 	struct inode *inode;
214 	struct romfs_inode ri;
215 	const char *name;		/* got from dentry */
216 	int len, ret;
217 
218 	offset = dir->i_ino & ROMFH_MASK;
219 	ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE);
220 	if (ret < 0)
221 		goto error;
222 
223 	/* search all the file entries in the list starting from the one
224 	 * pointed to by the directory's special data */
225 	maxoff = romfs_maxsize(dir->i_sb);
226 	offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
227 
228 	name = dentry->d_name.name;
229 	len = dentry->d_name.len;
230 
231 	for (;;) {
232 		if (!offset || offset >= maxoff)
233 			goto out0;
234 
235 		ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));
236 		if (ret < 0)
237 			goto error;
238 
239 		/* try to match the first 16 bytes of name */
240 		ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,
241 				       len);
242 		if (ret < 0)
243 			goto error;
244 		if (ret == 1)
245 			break;
246 
247 		/* next entry */
248 		offset = be32_to_cpu(ri.next) & ROMFH_MASK;
249 	}
250 
251 	/* Hard link handling */
252 	if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
253 		offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
254 
255 	inode = romfs_iget(dir->i_sb, offset);
256 	if (IS_ERR(inode)) {
257 		ret = PTR_ERR(inode);
258 		goto error;
259 	}
260 	goto outi;
261 
262 	/*
263 	 * it's a bit funky, _lookup needs to return an error code
264 	 * (negative) or a NULL, both as a dentry.  ENOENT should not
265 	 * be returned, instead we need to create a negative dentry by
266 	 * d_add(dentry, NULL); and return 0 as no error.
267 	 * (Although as I see, it only matters on writable file
268 	 * systems).
269 	 */
270 out0:
271 	inode = NULL;
272 outi:
273 	d_add(dentry, inode);
274 	ret = 0;
275 error:
276 	return ERR_PTR(ret);
277 }
278 
279 static const struct file_operations romfs_dir_operations = {
280 	.read		= generic_read_dir,
281 	.iterate	= romfs_readdir,
282 	.llseek		= default_llseek,
283 };
284 
285 static const struct inode_operations romfs_dir_inode_operations = {
286 	.lookup		= romfs_lookup,
287 };
288 
289 /*
290  * get a romfs inode based on its position in the image (which doubles as the
291  * inode number)
292  */
293 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
294 {
295 	struct romfs_inode_info *inode;
296 	struct romfs_inode ri;
297 	struct inode *i;
298 	unsigned long nlen;
299 	unsigned nextfh;
300 	int ret;
301 	umode_t mode;
302 
303 	/* we might have to traverse a chain of "hard link" file entries to get
304 	 * to the actual file */
305 	for (;;) {
306 		ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
307 		if (ret < 0)
308 			goto error;
309 
310 		/* XXX: do romfs_checksum here too (with name) */
311 
312 		nextfh = be32_to_cpu(ri.next);
313 		if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
314 			break;
315 
316 		pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
317 	}
318 
319 	/* determine the length of the filename */
320 	nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
321 	if (IS_ERR_VALUE(nlen))
322 		goto eio;
323 
324 	/* get an inode for this image position */
325 	i = iget_locked(sb, pos);
326 	if (!i)
327 		return ERR_PTR(-ENOMEM);
328 
329 	if (!(i->i_state & I_NEW))
330 		return i;
331 
332 	/* precalculate the data offset */
333 	inode = ROMFS_I(i);
334 	inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
335 	inode->i_dataoffset = pos + inode->i_metasize;
336 
337 	set_nlink(i, 1);		/* Hard to decide.. */
338 	i->i_size = be32_to_cpu(ri.size);
339 	i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
340 	i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
341 
342 	/* set up mode and ops */
343 	mode = romfs_modemap[nextfh & ROMFH_TYPE];
344 
345 	switch (nextfh & ROMFH_TYPE) {
346 	case ROMFH_DIR:
347 		i->i_size = ROMFS_I(i)->i_metasize;
348 		i->i_op = &romfs_dir_inode_operations;
349 		i->i_fop = &romfs_dir_operations;
350 		if (nextfh & ROMFH_EXEC)
351 			mode |= S_IXUGO;
352 		break;
353 	case ROMFH_REG:
354 		i->i_fop = &romfs_ro_fops;
355 		i->i_data.a_ops = &romfs_aops;
356 		if (i->i_sb->s_mtd)
357 			i->i_data.backing_dev_info =
358 				i->i_sb->s_mtd->backing_dev_info;
359 		if (nextfh & ROMFH_EXEC)
360 			mode |= S_IXUGO;
361 		break;
362 	case ROMFH_SYM:
363 		i->i_op = &page_symlink_inode_operations;
364 		i->i_data.a_ops = &romfs_aops;
365 		mode |= S_IRWXUGO;
366 		break;
367 	default:
368 		/* depending on MBZ for sock/fifos */
369 		nextfh = be32_to_cpu(ri.spec);
370 		init_special_inode(i, mode, MKDEV(nextfh >> 16,
371 						  nextfh & 0xffff));
372 		break;
373 	}
374 
375 	i->i_mode = mode;
376 
377 	unlock_new_inode(i);
378 	return i;
379 
380 eio:
381 	ret = -EIO;
382 error:
383 	printk(KERN_ERR "ROMFS: read error for inode 0x%lx\n", pos);
384 	return ERR_PTR(ret);
385 }
386 
387 /*
388  * allocate a new inode
389  */
390 static struct inode *romfs_alloc_inode(struct super_block *sb)
391 {
392 	struct romfs_inode_info *inode;
393 	inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
394 	return inode ? &inode->vfs_inode : NULL;
395 }
396 
397 /*
398  * return a spent inode to the slab cache
399  */
400 static void romfs_i_callback(struct rcu_head *head)
401 {
402 	struct inode *inode = container_of(head, struct inode, i_rcu);
403 	kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
404 }
405 
406 static void romfs_destroy_inode(struct inode *inode)
407 {
408 	call_rcu(&inode->i_rcu, romfs_i_callback);
409 }
410 
411 /*
412  * get filesystem statistics
413  */
414 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
415 {
416 	struct super_block *sb = dentry->d_sb;
417 	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
418 
419 	buf->f_type = ROMFS_MAGIC;
420 	buf->f_namelen = ROMFS_MAXFN;
421 	buf->f_bsize = ROMBSIZE;
422 	buf->f_bfree = buf->f_bavail = buf->f_ffree;
423 	buf->f_blocks =
424 		(romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;
425 	buf->f_fsid.val[0] = (u32)id;
426 	buf->f_fsid.val[1] = (u32)(id >> 32);
427 	return 0;
428 }
429 
430 /*
431  * remounting must involve read-only
432  */
433 static int romfs_remount(struct super_block *sb, int *flags, char *data)
434 {
435 	sync_filesystem(sb);
436 	*flags |= MS_RDONLY;
437 	return 0;
438 }
439 
440 static const struct super_operations romfs_super_ops = {
441 	.alloc_inode	= romfs_alloc_inode,
442 	.destroy_inode	= romfs_destroy_inode,
443 	.statfs		= romfs_statfs,
444 	.remount_fs	= romfs_remount,
445 };
446 
447 /*
448  * checksum check on part of a romfs filesystem
449  */
450 static __u32 romfs_checksum(const void *data, int size)
451 {
452 	const __be32 *ptr = data;
453 	__u32 sum;
454 
455 	sum = 0;
456 	size >>= 2;
457 	while (size > 0) {
458 		sum += be32_to_cpu(*ptr++);
459 		size--;
460 	}
461 	return sum;
462 }
463 
464 /*
465  * fill in the superblock
466  */
467 static int romfs_fill_super(struct super_block *sb, void *data, int silent)
468 {
469 	struct romfs_super_block *rsb;
470 	struct inode *root;
471 	unsigned long pos, img_size;
472 	const char *storage;
473 	size_t len;
474 	int ret;
475 
476 #ifdef CONFIG_BLOCK
477 	if (!sb->s_mtd) {
478 		sb_set_blocksize(sb, ROMBSIZE);
479 	} else {
480 		sb->s_blocksize = ROMBSIZE;
481 		sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
482 	}
483 #endif
484 
485 	sb->s_maxbytes = 0xFFFFFFFF;
486 	sb->s_magic = ROMFS_MAGIC;
487 	sb->s_flags |= MS_RDONLY | MS_NOATIME;
488 	sb->s_op = &romfs_super_ops;
489 
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 (!silent)
510 			printk(KERN_WARNING "VFS:"
511 			       " Can't find a romfs filesystem on dev %s.\n",
512 			       sb->s_id);
513 		goto error_rsb_inval;
514 	}
515 
516 	if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
517 		printk(KERN_ERR "ROMFS: bad initial checksum on dev %s.\n",
518 		       sb->s_id);
519 		goto error_rsb_inval;
520 	}
521 
522 	storage = sb->s_mtd ? "MTD" : "the block layer";
523 
524 	len = strnlen(rsb->name, ROMFS_MAXFN);
525 	if (!silent)
526 		printk(KERN_NOTICE "ROMFS: Mounting image '%*.*s' through %s\n",
527 		       (unsigned) len, (unsigned) len, rsb->name, storage);
528 
529 	kfree(rsb);
530 	rsb = NULL;
531 
532 	/* find the root directory */
533 	pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
534 
535 	root = romfs_iget(sb, pos);
536 	if (IS_ERR(root))
537 		return PTR_ERR(root);
538 
539 	sb->s_root = d_make_root(root);
540 	if (!sb->s_root)
541 		return -ENOMEM;
542 
543 	return 0;
544 
545 error_rsb_inval:
546 	ret = -EINVAL;
547 error_rsb:
548 	kfree(rsb);
549 	return ret;
550 }
551 
552 /*
553  * get a superblock for mounting
554  */
555 static struct dentry *romfs_mount(struct file_system_type *fs_type,
556 			int flags, const char *dev_name,
557 			void *data)
558 {
559 	struct dentry *ret = ERR_PTR(-EINVAL);
560 
561 #ifdef CONFIG_ROMFS_ON_MTD
562 	ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super);
563 #endif
564 #ifdef CONFIG_ROMFS_ON_BLOCK
565 	if (ret == ERR_PTR(-EINVAL))
566 		ret = mount_bdev(fs_type, flags, dev_name, data,
567 				  romfs_fill_super);
568 #endif
569 	return ret;
570 }
571 
572 /*
573  * destroy a romfs superblock in the appropriate manner
574  */
575 static void romfs_kill_sb(struct super_block *sb)
576 {
577 #ifdef CONFIG_ROMFS_ON_MTD
578 	if (sb->s_mtd) {
579 		kill_mtd_super(sb);
580 		return;
581 	}
582 #endif
583 #ifdef CONFIG_ROMFS_ON_BLOCK
584 	if (sb->s_bdev) {
585 		kill_block_super(sb);
586 		return;
587 	}
588 #endif
589 }
590 
591 static struct file_system_type romfs_fs_type = {
592 	.owner		= THIS_MODULE,
593 	.name		= "romfs",
594 	.mount		= romfs_mount,
595 	.kill_sb	= romfs_kill_sb,
596 	.fs_flags	= FS_REQUIRES_DEV,
597 };
598 MODULE_ALIAS_FS("romfs");
599 
600 /*
601  * inode storage initialiser
602  */
603 static void romfs_i_init_once(void *_inode)
604 {
605 	struct romfs_inode_info *inode = _inode;
606 
607 	inode_init_once(&inode->vfs_inode);
608 }
609 
610 /*
611  * romfs module initialisation
612  */
613 static int __init init_romfs_fs(void)
614 {
615 	int ret;
616 
617 	printk(KERN_INFO "ROMFS MTD (C) 2007 Red Hat, Inc.\n");
618 
619 	romfs_inode_cachep =
620 		kmem_cache_create("romfs_i",
621 				  sizeof(struct romfs_inode_info), 0,
622 				  SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
623 				  romfs_i_init_once);
624 
625 	if (!romfs_inode_cachep) {
626 		printk(KERN_ERR
627 		       "ROMFS error: Failed to initialise inode cache\n");
628 		return -ENOMEM;
629 	}
630 	ret = register_filesystem(&romfs_fs_type);
631 	if (ret) {
632 		printk(KERN_ERR "ROMFS error: Failed to register filesystem\n");
633 		goto error_register;
634 	}
635 	return 0;
636 
637 error_register:
638 	kmem_cache_destroy(romfs_inode_cachep);
639 	return ret;
640 }
641 
642 /*
643  * romfs module removal
644  */
645 static void __exit exit_romfs_fs(void)
646 {
647 	unregister_filesystem(&romfs_fs_type);
648 	/*
649 	 * Make sure all delayed rcu free inodes are flushed before we
650 	 * destroy cache.
651 	 */
652 	rcu_barrier();
653 	kmem_cache_destroy(romfs_inode_cachep);
654 }
655 
656 module_init(init_romfs_fs);
657 module_exit(exit_romfs_fs);
658 
659 MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
660 MODULE_AUTHOR("Red Hat, Inc.");
661 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */
662