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/parser.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
80 static struct kmem_cache *romfs_inode_cachep;
81
82 static 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
93 static 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
97 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos);
98
99 /*
100 * read a page worth of data from the image
101 */
romfs_readpage(struct file * file,struct page * page)102 static 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
144 static const struct address_space_operations romfs_aops = {
145 .readpage = romfs_readpage
146 };
147
148 /*
149 * read the entries from a directory
150 */
romfs_readdir(struct file * file,struct dir_context * ctx)151 static 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 }
205 out:
206 return 0;
207 }
208
209 /*
210 * look up an entry in a directory
211 */
romfs_lookup(struct inode * dir,struct dentry * dentry,unsigned int flags)212 static 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);
260 error:
261 return ERR_PTR(ret);
262 }
263
264 static const struct file_operations romfs_dir_operations = {
265 .read = generic_read_dir,
266 .iterate_shared = romfs_readdir,
267 .llseek = generic_file_llseek,
268 };
269
270 static 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 */
romfs_iget(struct super_block * sb,unsigned long pos)278 static 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
360 unlock_new_inode(i);
361 return i;
362
363 eio:
364 ret = -EIO;
365 error:
366 pr_err("read error for inode 0x%lx\n", pos);
367 return ERR_PTR(ret);
368 }
369
370 /*
371 * allocate a new inode
372 */
romfs_alloc_inode(struct super_block * sb)373 static struct inode *romfs_alloc_inode(struct super_block *sb)
374 {
375 struct romfs_inode_info *inode;
376
377 inode = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
378 return inode ? &inode->vfs_inode : NULL;
379 }
380
381 /*
382 * return a spent inode to the slab cache
383 */
romfs_i_callback(struct rcu_head * head)384 static void romfs_i_callback(struct rcu_head *head)
385 {
386 struct inode *inode = container_of(head, struct inode, i_rcu);
387
388 kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
389 }
390
romfs_destroy_inode(struct inode * inode)391 static void romfs_destroy_inode(struct inode *inode)
392 {
393 call_rcu(&inode->i_rcu, romfs_i_callback);
394 }
395
396 /*
397 * get filesystem statistics
398 */
romfs_statfs(struct dentry * dentry,struct kstatfs * buf)399 static int romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
400 {
401 struct super_block *sb = dentry->d_sb;
402 u64 id = 0;
403
404 /* When calling huge_encode_dev(),
405 * use sb->s_bdev->bd_dev when,
406 * - CONFIG_ROMFS_ON_BLOCK defined
407 * use sb->s_dev when,
408 * - CONFIG_ROMFS_ON_BLOCK undefined and
409 * - CONFIG_ROMFS_ON_MTD defined
410 * leave id as 0 when,
411 * - CONFIG_ROMFS_ON_BLOCK undefined and
412 * - CONFIG_ROMFS_ON_MTD undefined
413 */
414 if (sb->s_bdev)
415 id = huge_encode_dev(sb->s_bdev->bd_dev);
416 else if (sb->s_dev)
417 id = huge_encode_dev(sb->s_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 */
romfs_remount(struct super_block * sb,int * flags,char * data)433 static int romfs_remount(struct super_block *sb, int *flags, char *data)
434 {
435 sync_filesystem(sb);
436 *flags |= SB_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 */
romfs_checksum(const void * data,int size)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 */
romfs_fill_super(struct super_block * sb,void * data,int silent)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 |= SB_RDONLY | SB_NOATIME;
488 sb->s_op = &romfs_super_ops;
489
490 #ifdef CONFIG_ROMFS_ON_MTD
491 /* Use same dev ID from the underlying mtdblock device */
492 if (sb->s_mtd)
493 sb->s_dev = MKDEV(MTD_BLOCK_MAJOR, sb->s_mtd->index);
494 #endif
495 /* read the image superblock and check it */
496 rsb = kmalloc(512, GFP_KERNEL);
497 if (!rsb)
498 return -ENOMEM;
499
500 sb->s_fs_info = (void *) 512;
501 ret = romfs_dev_read(sb, 0, rsb, 512);
502 if (ret < 0)
503 goto error_rsb;
504
505 img_size = be32_to_cpu(rsb->size);
506
507 if (sb->s_mtd && img_size > sb->s_mtd->size)
508 goto error_rsb_inval;
509
510 sb->s_fs_info = (void *) img_size;
511
512 if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1 ||
513 img_size < ROMFH_SIZE) {
514 if (!silent)
515 pr_warn("VFS: Can't find a romfs filesystem on dev %s.\n",
516 sb->s_id);
517 goto error_rsb_inval;
518 }
519
520 if (romfs_checksum(rsb, min_t(size_t, img_size, 512))) {
521 pr_err("bad initial checksum on dev %s.\n", sb->s_id);
522 goto error_rsb_inval;
523 }
524
525 storage = sb->s_mtd ? "MTD" : "the block layer";
526
527 len = strnlen(rsb->name, ROMFS_MAXFN);
528 if (!silent)
529 pr_notice("Mounting image '%*.*s' through %s\n",
530 (unsigned) len, (unsigned) len, rsb->name, storage);
531
532 kfree(rsb);
533 rsb = NULL;
534
535 /* find the root directory */
536 pos = (ROMFH_SIZE + len + 1 + ROMFH_PAD) & ROMFH_MASK;
537
538 root = romfs_iget(sb, pos);
539 if (IS_ERR(root))
540 return PTR_ERR(root);
541
542 sb->s_root = d_make_root(root);
543 if (!sb->s_root)
544 return -ENOMEM;
545
546 return 0;
547
548 error_rsb_inval:
549 ret = -EINVAL;
550 error_rsb:
551 kfree(rsb);
552 return ret;
553 }
554
555 /*
556 * get a superblock for mounting
557 */
romfs_mount(struct file_system_type * fs_type,int flags,const char * dev_name,void * data)558 static struct dentry *romfs_mount(struct file_system_type *fs_type,
559 int flags, const char *dev_name,
560 void *data)
561 {
562 struct dentry *ret = ERR_PTR(-EINVAL);
563
564 #ifdef CONFIG_ROMFS_ON_MTD
565 ret = mount_mtd(fs_type, flags, dev_name, data, romfs_fill_super);
566 #endif
567 #ifdef CONFIG_ROMFS_ON_BLOCK
568 if (ret == ERR_PTR(-EINVAL))
569 ret = mount_bdev(fs_type, flags, dev_name, data,
570 romfs_fill_super);
571 #endif
572 return ret;
573 }
574
575 /*
576 * destroy a romfs superblock in the appropriate manner
577 */
romfs_kill_sb(struct super_block * sb)578 static void romfs_kill_sb(struct super_block *sb)
579 {
580 #ifdef CONFIG_ROMFS_ON_MTD
581 if (sb->s_mtd) {
582 kill_mtd_super(sb);
583 return;
584 }
585 #endif
586 #ifdef CONFIG_ROMFS_ON_BLOCK
587 if (sb->s_bdev) {
588 kill_block_super(sb);
589 return;
590 }
591 #endif
592 }
593
594 static struct file_system_type romfs_fs_type = {
595 .owner = THIS_MODULE,
596 .name = "romfs",
597 .mount = romfs_mount,
598 .kill_sb = romfs_kill_sb,
599 .fs_flags = FS_REQUIRES_DEV,
600 };
601 MODULE_ALIAS_FS("romfs");
602
603 /*
604 * inode storage initialiser
605 */
romfs_i_init_once(void * _inode)606 static 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 */
init_romfs_fs(void)616 static int __init init_romfs_fs(void)
617 {
618 int ret;
619
620 pr_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 SLAB_ACCOUNT, romfs_i_init_once);
627
628 if (!romfs_inode_cachep) {
629 pr_err("Failed to initialise inode cache\n");
630 return -ENOMEM;
631 }
632 ret = register_filesystem(&romfs_fs_type);
633 if (ret) {
634 pr_err("Failed to register filesystem\n");
635 goto error_register;
636 }
637 return 0;
638
639 error_register:
640 kmem_cache_destroy(romfs_inode_cachep);
641 return ret;
642 }
643
644 /*
645 * romfs module removal
646 */
exit_romfs_fs(void)647 static void __exit exit_romfs_fs(void)
648 {
649 unregister_filesystem(&romfs_fs_type);
650 /*
651 * Make sure all delayed rcu free inodes are flushed before we
652 * destroy cache.
653 */
654 rcu_barrier();
655 kmem_cache_destroy(romfs_inode_cachep);
656 }
657
658 module_init(init_romfs_fs);
659 module_exit(exit_romfs_fs);
660
661 MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
662 MODULE_AUTHOR("Red Hat, Inc.");
663 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */
664
