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
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_read_folio(struct file * file,struct folio * folio)102 static int romfs_read_folio(struct file *file, struct folio *folio)
103 {
104 struct page *page = &folio->page;
105 struct inode *inode = page->mapping->host;
106 loff_t offset, size;
107 unsigned long fillsize, pos;
108 void *buf;
109 int ret;
110
111 buf = kmap(page);
112 if (!buf)
113 return -ENOMEM;
114
115 /* 32 bit warning -- but not for us :) */
116 offset = page_offset(page);
117 size = i_size_read(inode);
118 fillsize = 0;
119 ret = 0;
120 if (offset < size) {
121 size -= offset;
122 fillsize = size > PAGE_SIZE ? PAGE_SIZE : size;
123
124 pos = ROMFS_I(inode)->i_dataoffset + offset;
125
126 ret = romfs_dev_read(inode->i_sb, pos, buf, fillsize);
127 if (ret < 0) {
128 SetPageError(page);
129 fillsize = 0;
130 ret = -EIO;
131 }
132 }
133
134 if (fillsize < PAGE_SIZE)
135 memset(buf + fillsize, 0, PAGE_SIZE - fillsize);
136 if (ret == 0)
137 SetPageUptodate(page);
138
139 flush_dcache_page(page);
140 kunmap(page);
141 unlock_page(page);
142 return ret;
143 }
144
145 static const struct address_space_operations romfs_aops = {
146 .read_folio = romfs_read_folio
147 };
148
149 /*
150 * read the entries from a directory
151 */
romfs_readdir(struct file * file,struct dir_context * ctx)152 static int romfs_readdir(struct file *file, struct dir_context *ctx)
153 {
154 struct inode *i = file_inode(file);
155 struct romfs_inode ri;
156 unsigned long offset, maxoff;
157 int j, ino, nextfh;
158 char fsname[ROMFS_MAXFN]; /* XXX dynamic? */
159 int ret;
160
161 maxoff = romfs_maxsize(i->i_sb);
162
163 offset = ctx->pos;
164 if (!offset) {
165 offset = i->i_ino & ROMFH_MASK;
166 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
167 if (ret < 0)
168 goto out;
169 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
170 }
171
172 /* Not really failsafe, but we are read-only... */
173 for (;;) {
174 if (!offset || offset >= maxoff) {
175 offset = maxoff;
176 ctx->pos = offset;
177 goto out;
178 }
179 ctx->pos = offset;
180
181 /* Fetch inode info */
182 ret = romfs_dev_read(i->i_sb, offset, &ri, ROMFH_SIZE);
183 if (ret < 0)
184 goto out;
185
186 j = romfs_dev_strnlen(i->i_sb, offset + ROMFH_SIZE,
187 sizeof(fsname) - 1);
188 if (j < 0)
189 goto out;
190
191 ret = romfs_dev_read(i->i_sb, offset + ROMFH_SIZE, fsname, j);
192 if (ret < 0)
193 goto out;
194 fsname[j] = '\0';
195
196 ino = offset;
197 nextfh = be32_to_cpu(ri.next);
198 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
199 ino = be32_to_cpu(ri.spec);
200 if (!dir_emit(ctx, fsname, j, ino,
201 romfs_dtype_table[nextfh & ROMFH_TYPE]))
202 goto out;
203
204 offset = nextfh & ROMFH_MASK;
205 }
206 out:
207 return 0;
208 }
209
210 /*
211 * look up an entry in a directory
212 */
romfs_lookup(struct inode * dir,struct dentry * dentry,unsigned int flags)213 static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
214 unsigned int flags)
215 {
216 unsigned long offset, maxoff;
217 struct inode *inode = NULL;
218 struct romfs_inode ri;
219 const char *name; /* got from dentry */
220 int len, ret;
221
222 offset = dir->i_ino & ROMFH_MASK;
223 ret = romfs_dev_read(dir->i_sb, offset, &ri, ROMFH_SIZE);
224 if (ret < 0)
225 goto error;
226
227 /* search all the file entries in the list starting from the one
228 * pointed to by the directory's special data */
229 maxoff = romfs_maxsize(dir->i_sb);
230 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
231
232 name = dentry->d_name.name;
233 len = dentry->d_name.len;
234
235 for (;;) {
236 if (!offset || offset >= maxoff)
237 break;
238
239 ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));
240 if (ret < 0)
241 goto error;
242
243 /* try to match the first 16 bytes of name */
244 ret = romfs_dev_strcmp(dir->i_sb, offset + ROMFH_SIZE, name,
245 len);
246 if (ret < 0)
247 goto error;
248 if (ret == 1) {
249 /* Hard link handling */
250 if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
251 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
252 inode = romfs_iget(dir->i_sb, offset);
253 break;
254 }
255
256 /* next entry */
257 offset = be32_to_cpu(ri.next) & ROMFH_MASK;
258 }
259
260 return d_splice_alias(inode, dentry);
261 error:
262 return ERR_PTR(ret);
263 }
264
265 static const struct file_operations romfs_dir_operations = {
266 .read = generic_read_dir,
267 .iterate_shared = romfs_readdir,
268 .llseek = generic_file_llseek,
269 };
270
271 static const struct inode_operations romfs_dir_inode_operations = {
272 .lookup = romfs_lookup,
273 };
274
275 /*
276 * get a romfs inode based on its position in the image (which doubles as the
277 * inode number)
278 */
romfs_iget(struct super_block * sb,unsigned long pos)279 static struct inode *romfs_iget(struct super_block *sb, unsigned long pos)
280 {
281 struct romfs_inode_info *inode;
282 struct romfs_inode ri;
283 struct inode *i;
284 unsigned long nlen;
285 unsigned nextfh;
286 int ret;
287 umode_t mode;
288
289 /* we might have to traverse a chain of "hard link" file entries to get
290 * to the actual file */
291 for (;;) {
292 ret = romfs_dev_read(sb, pos, &ri, sizeof(ri));
293 if (ret < 0)
294 goto error;
295
296 /* XXX: do romfs_checksum here too (with name) */
297
298 nextfh = be32_to_cpu(ri.next);
299 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
300 break;
301
302 pos = be32_to_cpu(ri.spec) & ROMFH_MASK;
303 }
304
305 /* determine the length of the filename */
306 nlen = romfs_dev_strnlen(sb, pos + ROMFH_SIZE, ROMFS_MAXFN);
307 if (IS_ERR_VALUE(nlen))
308 goto eio;
309
310 /* get an inode for this image position */
311 i = iget_locked(sb, pos);
312 if (!i)
313 return ERR_PTR(-ENOMEM);
314
315 if (!(i->i_state & I_NEW))
316 return i;
317
318 /* precalculate the data offset */
319 inode = ROMFS_I(i);
320 inode->i_metasize = (ROMFH_SIZE + nlen + 1 + ROMFH_PAD) & ROMFH_MASK;
321 inode->i_dataoffset = pos + inode->i_metasize;
322
323 set_nlink(i, 1); /* Hard to decide.. */
324 i->i_size = be32_to_cpu(ri.size);
325 i->i_mtime = i->i_atime = inode_set_ctime(i, 0, 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
364 eio:
365 ret = -EIO;
366 error:
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 */
romfs_alloc_inode(struct super_block * sb)374 static struct inode *romfs_alloc_inode(struct super_block *sb)
375 {
376 struct romfs_inode_info *inode;
377
378 inode = alloc_inode_sb(sb, 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 */
romfs_free_inode(struct inode * inode)385 static 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 */
romfs_statfs(struct dentry * dentry,struct kstatfs * buf)393 static 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 */
romfs_reconfigure(struct fs_context * fc)426 static 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
433 static 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 */
romfs_checksum(const void * data,int size)442 static __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 */
romfs_fill_super(struct super_block * sb,struct fs_context * fc)459 static 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
542 error_rsb_inval:
543 ret = -EINVAL;
544 error_rsb:
545 kfree(rsb);
546 return ret;
547 }
548
549 /*
550 * get a superblock for mounting
551 */
romfs_get_tree(struct fs_context * fc)552 static 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
566 static 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 */
romfs_init_fs_context(struct fs_context * fc)574 static 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 */
romfs_kill_sb(struct super_block * sb)583 static void romfs_kill_sb(struct super_block *sb)
584 {
585 generic_shutdown_super(sb);
586
587 #ifdef CONFIG_ROMFS_ON_MTD
588 if (sb->s_mtd) {
589 put_mtd_device(sb->s_mtd);
590 sb->s_mtd = NULL;
591 }
592 #endif
593 #ifdef CONFIG_ROMFS_ON_BLOCK
594 if (sb->s_bdev) {
595 sync_blockdev(sb->s_bdev);
596 blkdev_put(sb->s_bdev, sb);
597 }
598 #endif
599 }
600
601 static struct file_system_type romfs_fs_type = {
602 .owner = THIS_MODULE,
603 .name = "romfs",
604 .init_fs_context = romfs_init_fs_context,
605 .kill_sb = romfs_kill_sb,
606 .fs_flags = FS_REQUIRES_DEV,
607 };
608 MODULE_ALIAS_FS("romfs");
609
610 /*
611 * inode storage initialiser
612 */
romfs_i_init_once(void * _inode)613 static void romfs_i_init_once(void *_inode)
614 {
615 struct romfs_inode_info *inode = _inode;
616
617 inode_init_once(&inode->vfs_inode);
618 }
619
620 /*
621 * romfs module initialisation
622 */
init_romfs_fs(void)623 static int __init init_romfs_fs(void)
624 {
625 int ret;
626
627 pr_info("ROMFS MTD (C) 2007 Red Hat, Inc.\n");
628
629 romfs_inode_cachep =
630 kmem_cache_create("romfs_i",
631 sizeof(struct romfs_inode_info), 0,
632 SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD |
633 SLAB_ACCOUNT, romfs_i_init_once);
634
635 if (!romfs_inode_cachep) {
636 pr_err("Failed to initialise inode cache\n");
637 return -ENOMEM;
638 }
639 ret = register_filesystem(&romfs_fs_type);
640 if (ret) {
641 pr_err("Failed to register filesystem\n");
642 goto error_register;
643 }
644 return 0;
645
646 error_register:
647 kmem_cache_destroy(romfs_inode_cachep);
648 return ret;
649 }
650
651 /*
652 * romfs module removal
653 */
exit_romfs_fs(void)654 static void __exit exit_romfs_fs(void)
655 {
656 unregister_filesystem(&romfs_fs_type);
657 /*
658 * Make sure all delayed rcu free inodes are flushed before we
659 * destroy cache.
660 */
661 rcu_barrier();
662 kmem_cache_destroy(romfs_inode_cachep);
663 }
664
665 module_init(init_romfs_fs);
666 module_exit(exit_romfs_fs);
667
668 MODULE_DESCRIPTION("Direct-MTD Capable RomFS");
669 MODULE_AUTHOR("Red Hat, Inc.");
670 MODULE_LICENSE("GPL"); /* Actually dual-licensed, but it doesn't matter for */
671