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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]; /* XXX dynamic? */
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 .llseek = default_llseek,
286};
287
288static const struct inode_operations romfs_dir_inode_operations = {
289 .lookup = romfs_lookup,
290};
291
292/*
293 * get a romfs inode based on its position in the image (which doubles as the
294 * inode number)
295 */
296static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
297{
298 struct romfs_inode_info *inode;
299 struct romfs_inode ri;
300 struct inode *i;
301 unsigned long nlen;
302 unsigned nextfh;
303 int ret;
304 umode_t mode;
305
306 /* we might have to traverse a chain of "hard link" file entries to get
307 * to the actual file */
308 for (;;) {
309 ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
310 if (ret < 0)
311 goto error;
312
313 /* XXX: do romfs_checksum here too (with name) */
314
315 nextfh = be32_to_cpu(ri.next);
316 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
317 break;
318
319 pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
320 }
321
322 /* determine the length of the filename */
323 nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
324 if (IS_ERR_VALUE(nlen))
325 goto eio;
326
327 /* get an inode for this image position */
328 i = iget_locked(sb, pos);
329 if (!i)
330 return ERR_PTR(-ENOMEM);
331
332 if (!(i->i_state & I_NEW))
333 return i;
334
335 /* precalculate the data offset */
336 inode = ROMFS_I(i);
337 inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
338 inode->i_dataoffset = pos + inode->i_metasize;
339
340 set_nlink(i, 1); /* Hard to decide.. */
341 i->i_size = be32_to_cpu(ri.size);
342 i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
343 i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
344
345 /* set up mode and ops */
346 mode = romfs_modemap[nextfh & ROMFH_TYPE];
347
348 switch (nextfh & ROMFH_TYPE) {
349 case ROMFH_DIR:
350 i->i_size = ROMFS_I(i)->i_metasize;
351 i->i_op = &romfs_dir_inode_operations;
352 i->i_fop = &romfs_dir_operations;
353 if (nextfh & ROMFH_EXEC)
354 mode |= S_IXUGO;
355 break;
356 case ROMFH_REG:
357 i->i_fop = &romfs_ro_fops;
358 i->i_data.a_ops = &romfs_aops;
359 if (i->i_sb->s_mtd)
360 i->i_data.backing_dev_info =
361 i->i_sb->s_mtd->backing_dev_info;
362 if (nextfh & ROMFH_EXEC)
363 mode |= S_IXUGO;
364 break;
365 case ROMFH_SYM:
366 i->i_op = &page_symlink_inode_operations;
367 i->i_data.a_ops = &romfs_aops;
368 mode |= S_IRWXUGO;
369 break;
370 default:
371 /* depending on MBZ for sock/fifos */
372 nextfh = be32_to_cpu(ri.spec);
373 init_special_inode(i, mode, MKDEV(nextfh >> 16,
374 nextfh & 0xffff));
375 break;
376 }
377
378 i->i_mode = mode;
379
380 unlock_new_inode(i);
381 return i;
382
383eio:
384 ret = -EIO;
385error:
386 printk(KERN_ERR "ROMFS: read error for inode 0x%lx\n", pos);
387 return ERR_PTR(ret);
388}
389
390/*
391 * allocate a new inode
392 */
393static struct inode *romfs_alloc_inode(struct super_block *sb)
394{
395 struct romfs_inode_info *inode;
396 inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
397 return inode ? &inode->vfs_inode : NULL;
398}
399
400/*
401 * return a spent inode to the slab cache
402 */
403static void romfs_i_callback(struct rcu_head *head)
404{
405 struct inode *inode = container_of(head, struct inode, i_rcu);
406 kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
407}
408
409static void romfs_destroy_inode(struct inode *inode)
410{
411 call_rcu(&inode->i_rcu, romfs_i_callback);
412}
413
414/*
415 * get filesystem statistics
416 */
417static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
418{
419 struct super_block *sb = dentry->d_sb;
420 u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
421
422 buf->f_type = ROMFS_MAGIC;
423 buf->f_namelen = ROMFS_MAXFN;
424 buf->f_bsize = ROMBSIZE;
425 buf->f_bfree = buf->f_bavail = buf->f_ffree;
426 buf->f_blocks =
427 (romfs_maxsize(dentry->d_sb) + ROMBSIZE - 1) >> ROMBSBITS;
428 buf->f_fsid.val[0] = (u32)id;
429 buf->f_fsid.val[1] = (u32)(id >> 32);
430 return 0;
431}
432
433/*
434 * remounting must involve read-only
435 */
436static int romfs_remount(struct super_block *sb, int *flags, char *data)
437{
438 *flags |= MS_RDONLY;
439 return 0;
440}
441
442static const struct super_operations romfs_super_ops = {
443 .alloc_inode = romfs_alloc_inode,
444 .destroy_inode = romfs_destroy_inode,
445 .statfs = romfs_statfs,
446 .remount_fs = romfs_remount,
447};
448
449/*
450 * checksum check on part of a romfs filesystem
451 */
452static __u32 romfs_checksum(const void *data, int size)
453{
454 const __be32 *ptr = data;
455 __u32 sum;
456
457 sum = 0;
458 size >>= 2;
459 while (size > 0) {
460 sum += be32_to_cpu(*ptr++);
461 size--;
462 }
463 return sum;
464}
465
466/*
467 * fill in the superblock
468 */
469static int romfs_fill_super(struct super_block *sb, void *data, int silent)
470{
471 struct romfs_super_block *rsb;
472 struct inode *root;
473 unsigned long pos, img_size;
474 const char *storage;
475 size_t len;
476 int ret;
477
478#ifdef CONFIG_BLOCK
479 if (!sb->s_mtd) {
480 sb_set_blocksize(sb, ROMBSIZE);
481 } else {
482 sb->s_blocksize = ROMBSIZE;
483 sb->s_blocksize_bits = blksize_bits(ROMBSIZE);
484 }
485#endif
486
487 sb->s_maxbytes = 0xFFFFFFFF;
488 sb->s_magic = ROMFS_MAGIC;
489 sb->s_flags |= MS_RDONLY | MS_NOATIME;
490 sb->s_op = &romfs_super_ops;
491
492 /* read the image superblock and check it */
493 rsb = kmalloc(512, GFP_KERNEL);
494 if (!rsb)
495 return -ENOMEM;
496
497 sb->s_fs_info = (void *) 512;
498 ret = romfs_dev_read(sb, 0, rsb, 512);
499 if (ret < 0)
500 goto error_rsb;
501
502 img_size = be32_to_cpu(rsb->size);
503
504 if (sb->s_mtd && img_size > sb->s_mtd->size)
505 goto error_rsb_inval;
506
507 sb->s_fs_info = (void *) img_size;
508
509 if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
510 img_size < ROMFH_SIZE) {
511 if (!silent)
512 printk(KERN_WARNING "VFS:"
513 " Can't find a romfs filesystem on dev %s.\n",
514 sb->s_id);
515 goto error_rsb_inval;
516 }
517
518 if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
519 printk(KERN_ERR "ROMFS: bad initial checksum on dev %s.\n",
520 sb->s_id);
521 goto error_rsb_inval;
522 }
523
524 storage = sb->s_mtd ? "MTD" : "the block layer";
525
526 len = strnlen(rsb->name, ROMFS_MAXFN);
527 if (!silent)
528 printk(KERN_NOTICE "ROMFS: Mounting image '%*.*s' through %s\n",
529 (unsigned) len, (unsigned) len, rsb->name, storage);
530
531 kfree(rsb);
532 rsb = NULL;
533
534 /* find the root directory */
535 pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
536
537 root = romfs_iget(sb, pos);
538 if (IS_ERR(root))
539 goto error;
540
541 sb->s_root = d_make_root(root);
542 if (!sb->s_root)
543 goto error;
544
545 return 0;
546
547error:
548 return -EINVAL;
549error_rsb_inval:
550 ret = -EINVAL;
551error_rsb:
552 kfree(rsb);
553 return ret;
554}
555
556/*
557 * get a superblock for mounting
558 */
559static struct dentry *romfs_mount(struct file_system_type *fs_type,
560 int flags, const char *dev_name,
561 void *data)
562{
563 struct dentry *ret = ERR_PTR(-EINVAL);
564
565#ifdef CONFIG_ROMFS_ON_MTD
566 ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super);
567#endif
568#ifdef CONFIG_ROMFS_ON_BLOCK
569 if (ret == ERR_PTR(-EINVAL))
570 ret = mount_bdev(fs_type, flags, dev_name, data,
571 romfs_fill_super);
572#endif
573 return ret;
574}
575
576/*
577 * destroy a romfs superblock in the appropriate manner
578 */
579static void romfs_kill_sb(struct super_block *sb)
580{
581#ifdef CONFIG_ROMFS_ON_MTD
582 if (sb->s_mtd) {
583 kill_mtd_super(sb);
584 return;
585 }
586#endif
587#ifdef CONFIG_ROMFS_ON_BLOCK
588 if (sb->s_bdev) {
589 kill_block_super(sb);
590 return;
591 }
592#endif
593}
594
595static struct file_system_type romfs_fs_type = {
596 .owner = THIS_MODULE,
597 .name = "romfs",
598 .mount = romfs_mount,
599 .kill_sb = romfs_kill_sb,
600 .fs_flags = FS_REQUIRES_DEV,
601};
602
603/*
604 * inode storage initialiser
605 */
606static void romfs_i_init_once(void *_inode)
607{
608 struct romfs_inode_info *inode = _inode;
609
610 inode_init_once(&inode->vfs_inode);
611}
612
613/*
614 * romfs module initialisation
615 */
616static int __init init_romfs_fs(void)
617{
618 int ret;
619
620 printk(KERN_INFO "ROMFS MTD (C) 2007 Red Hat, Inc.\n");
621
622 romfs_inode_cachep =
623 kmem_cache_create("romfs_i",
624 sizeof(struct romfs_inode_info), 0,
625 SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
626 romfs_i_init_once);
627
628 if (!romfs_inode_cachep) {
629 printk(KERN_ERR
630 "ROMFS error: Failed to initialise inode cache\n");
631 return -ENOMEM;
632 }
633 ret = register_filesystem(&romfs_fs_type);
634 if (ret) {
635 printk(KERN_ERR "ROMFS error: 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 kmem_cache_destroy(romfs_inode_cachep);
652}
653
654module_init(init_romfs_fs);
655module_exit(exit_romfs_fs);
656
657MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
658MODULE_AUTHOR("Red Hat, Inc.");
659MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */