1 /*
2 * ROMFS file system, Linux implementation
3 *
4 * Copyright (C) 1997-1999 Janos Farkas <chexum@shadow.banki.hu>
5 *
6 * Using parts of the minix filesystem
7 * Copyright (C) 1991, 1992 Linus Torvalds
8 *
9 * and parts of the affs filesystem additionally
10 * Copyright (C) 1993 Ray Burr
11 * Copyright (C) 1996 Hans-Joachim Widmaier
12 *
13 * This program is free software; you can redistribute it and/or
14 * modify it under the terms of the GNU General Public License
15 * as published by the Free Software Foundation; either version
16 * 2 of the License, or (at your option) any later version.
17 *
18 * Changes
19 * Changed for 2.1.19 modules
20 * Jan 1997 Initial release
21 * Jun 1997 2.1.43+ changes
22 * Proper page locking in readpage
23 * Changed to work with 2.1.45+ fs
24 * Jul 1997 Fixed follow_link
25 * 2.1.47
26 * lookup shouldn't return -ENOENT
27 * from Horst von Brand:
28 * fail on wrong checksum
29 * double unlock_super was possible
30 * correct namelen for statfs
31 * spotted by Bill Hawes:
32 * readlink shouldn't iput()
33 * Jun 1998 2.1.106 from Avery Pennarun: glibc scandir()
34 * exposed a problem in readdir
35 * 2.1.107 code-freeze spellchecker run
36 * Aug 1998 2.1.118+ VFS changes
37 * Sep 1998 2.1.122 another VFS change (follow_link)
38 * Apr 1999 2.2.7 no more EBADF checking in
39 * lookup/readdir, use ERR_PTR
40 * Jun 1999 2.3.6 d_alloc_root use changed
41 * 2.3.9 clean up usage of ENOENT/negative
42 * dentries in lookup
43 * clean up page flags setting
44 * (error, uptodate, locking) in
45 * in readpage
46 * use init_special_inode for
47 * fifos/sockets (and streamline) in
48 * read_inode, fix _ops table order
49 * Aug 1999 2.3.16 __initfunc() => __init change
50 * Oct 1999 2.3.24 page->owner hack obsoleted
51 * Nov 1999 2.3.27 2.3.25+ page->offset => index change
52 */
53
54 /* todo:
55 * - see Documentation/filesystems/romfs.txt
56 * - use allocated, not stack memory for file names?
57 * - considering write access...
58 * - network (tftp) files?
59 * - merge back some _op tables
60 */
61
62 /*
63 * Sorry about some optimizations and for some goto's. I just wanted
64 * to squeeze some more bytes out of this code.. :)
65 */
66
67 #include <linux/module.h>
68 #include <linux/types.h>
69 #include <linux/errno.h>
70 #include <linux/slab.h>
71 #include <linux/romfs_fs.h>
72 #include <linux/fs.h>
73 #include <linux/init.h>
74 #include <linux/pagemap.h>
75 #include <linux/smp_lock.h>
76 #include <linux/buffer_head.h>
77 #include <linux/vfs.h>
78
79 #include <asm/uaccess.h>
80
81 struct romfs_inode_info {
82 unsigned long i_metasize; /* size of non-data area */
83 unsigned long i_dataoffset; /* from the start of fs */
84 struct inode vfs_inode;
85 };
86
87 static struct inode *romfs_iget(struct super_block *, unsigned long);
88
89 /* instead of private superblock data */
romfs_maxsize(struct super_block * sb)90 static inline unsigned long romfs_maxsize(struct super_block *sb)
91 {
92 return (unsigned long)sb->s_fs_info;
93 }
94
ROMFS_I(struct inode * inode)95 static inline struct romfs_inode_info *ROMFS_I(struct inode *inode)
96 {
97 return container_of(inode, struct romfs_inode_info, vfs_inode);
98 }
99
100 static __u32
romfs_checksum(void * data,int size)101 romfs_checksum(void *data, int size)
102 {
103 __u32 sum;
104 __be32 *ptr;
105
106 sum = 0; ptr = data;
107 size>>=2;
108 while (size>0) {
109 sum += be32_to_cpu(*ptr++);
110 size--;
111 }
112 return sum;
113 }
114
115 static const struct super_operations romfs_ops;
116
romfs_fill_super(struct super_block * s,void * data,int silent)117 static int romfs_fill_super(struct super_block *s, void *data, int silent)
118 {
119 struct buffer_head *bh;
120 struct romfs_super_block *rsb;
121 struct inode *root;
122 int sz, ret = -EINVAL;
123
124 /* I would parse the options here, but there are none.. :) */
125
126 sb_set_blocksize(s, ROMBSIZE);
127 s->s_maxbytes = 0xFFFFFFFF;
128
129 bh = sb_bread(s, 0);
130 if (!bh) {
131 /* XXX merge with other printk? */
132 printk ("romfs: unable to read superblock\n");
133 goto outnobh;
134 }
135
136 rsb = (struct romfs_super_block *)bh->b_data;
137 sz = be32_to_cpu(rsb->size);
138 if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1
139 || sz < ROMFH_SIZE) {
140 if (!silent)
141 printk ("VFS: Can't find a romfs filesystem on dev "
142 "%s.\n", s->s_id);
143 goto out;
144 }
145 if (romfs_checksum(rsb, min_t(int, sz, 512))) {
146 printk ("romfs: bad initial checksum on dev "
147 "%s.\n", s->s_id);
148 goto out;
149 }
150
151 s->s_magic = ROMFS_MAGIC;
152 s->s_fs_info = (void *)(long)sz;
153
154 s->s_flags |= MS_RDONLY;
155
156 /* Find the start of the fs */
157 sz = (ROMFH_SIZE +
158 strnlen(rsb->name, ROMFS_MAXFN) + 1 + ROMFH_PAD)
159 & ROMFH_MASK;
160
161 s->s_op = &romfs_ops;
162 root = romfs_iget(s, sz);
163 if (IS_ERR(root)) {
164 ret = PTR_ERR(root);
165 goto out;
166 }
167
168 ret = -ENOMEM;
169 s->s_root = d_alloc_root(root);
170 if (!s->s_root)
171 goto outiput;
172
173 brelse(bh);
174 return 0;
175
176 outiput:
177 iput(root);
178 out:
179 brelse(bh);
180 outnobh:
181 return ret;
182 }
183
184 /* That's simple too. */
185
186 static int
romfs_statfs(struct dentry * dentry,struct kstatfs * buf)187 romfs_statfs(struct dentry *dentry, struct kstatfs *buf)
188 {
189 buf->f_type = ROMFS_MAGIC;
190 buf->f_bsize = ROMBSIZE;
191 buf->f_bfree = buf->f_bavail = buf->f_ffree;
192 buf->f_blocks = (romfs_maxsize(dentry->d_sb)+ROMBSIZE-1)>>ROMBSBITS;
193 buf->f_namelen = ROMFS_MAXFN;
194 return 0;
195 }
196
197 /* some helper routines */
198
199 static int
romfs_strnlen(struct inode * i,unsigned long offset,unsigned long count)200 romfs_strnlen(struct inode *i, unsigned long offset, unsigned long count)
201 {
202 struct buffer_head *bh;
203 unsigned long avail, maxsize, res;
204
205 maxsize = romfs_maxsize(i->i_sb);
206 if (offset >= maxsize)
207 return -1;
208
209 /* strnlen is almost always valid */
210 if (count > maxsize || offset+count > maxsize)
211 count = maxsize-offset;
212
213 bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
214 if (!bh)
215 return -1; /* error */
216
217 avail = ROMBSIZE - (offset & ROMBMASK);
218 maxsize = min_t(unsigned long, count, avail);
219 res = strnlen(((char *)bh->b_data)+(offset&ROMBMASK), maxsize);
220 brelse(bh);
221
222 if (res < maxsize)
223 return res; /* found all of it */
224
225 while (res < count) {
226 offset += maxsize;
227
228 bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
229 if (!bh)
230 return -1;
231 maxsize = min_t(unsigned long, count - res, ROMBSIZE);
232 avail = strnlen(bh->b_data, maxsize);
233 res += avail;
234 brelse(bh);
235 if (avail < maxsize)
236 return res;
237 }
238 return res;
239 }
240
241 static int
romfs_copyfrom(struct inode * i,void * dest,unsigned long offset,unsigned long count)242 romfs_copyfrom(struct inode *i, void *dest, unsigned long offset, unsigned long count)
243 {
244 struct buffer_head *bh;
245 unsigned long avail, maxsize, res;
246
247 maxsize = romfs_maxsize(i->i_sb);
248 if (offset >= maxsize || count > maxsize || offset+count>maxsize)
249 return -1;
250
251 bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
252 if (!bh)
253 return -1; /* error */
254
255 avail = ROMBSIZE - (offset & ROMBMASK);
256 maxsize = min_t(unsigned long, count, avail);
257 memcpy(dest, ((char *)bh->b_data) + (offset & ROMBMASK), maxsize);
258 brelse(bh);
259
260 res = maxsize; /* all of it */
261
262 while (res < count) {
263 offset += maxsize;
264 dest += maxsize;
265
266 bh = sb_bread(i->i_sb, offset>>ROMBSBITS);
267 if (!bh)
268 return -1;
269 maxsize = min_t(unsigned long, count - res, ROMBSIZE);
270 memcpy(dest, bh->b_data, maxsize);
271 brelse(bh);
272 res += maxsize;
273 }
274 return res;
275 }
276
277 static unsigned char romfs_dtype_table[] = {
278 DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
279 };
280
281 static int
romfs_readdir(struct file * filp,void * dirent,filldir_t filldir)282 romfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
283 {
284 struct inode *i = filp->f_path.dentry->d_inode;
285 struct romfs_inode ri;
286 unsigned long offset, maxoff;
287 int j, ino, nextfh;
288 int stored = 0;
289 char fsname[ROMFS_MAXFN]; /* XXX dynamic? */
290
291 lock_kernel();
292
293 maxoff = romfs_maxsize(i->i_sb);
294
295 offset = filp->f_pos;
296 if (!offset) {
297 offset = i->i_ino & ROMFH_MASK;
298 if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 0)
299 goto out;
300 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
301 }
302
303 /* Not really failsafe, but we are read-only... */
304 for(;;) {
305 if (!offset || offset >= maxoff) {
306 offset = maxoff;
307 filp->f_pos = offset;
308 goto out;
309 }
310 filp->f_pos = offset;
311
312 /* Fetch inode info */
313 if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 0)
314 goto out;
315
316 j = romfs_strnlen(i, offset+ROMFH_SIZE, sizeof(fsname)-1);
317 if (j < 0)
318 goto out;
319
320 fsname[j]=0;
321 romfs_copyfrom(i, fsname, offset+ROMFH_SIZE, j);
322
323 ino = offset;
324 nextfh = be32_to_cpu(ri.next);
325 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
326 ino = be32_to_cpu(ri.spec);
327 if (filldir(dirent, fsname, j, offset, ino,
328 romfs_dtype_table[nextfh & ROMFH_TYPE]) < 0) {
329 goto out;
330 }
331 stored++;
332 offset = nextfh & ROMFH_MASK;
333 }
334 out:
335 unlock_kernel();
336 return stored;
337 }
338
339 static struct dentry *
romfs_lookup(struct inode * dir,struct dentry * dentry,struct nameidata * nd)340 romfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
341 {
342 unsigned long offset, maxoff;
343 long res;
344 int fslen;
345 struct inode *inode = NULL;
346 char fsname[ROMFS_MAXFN]; /* XXX dynamic? */
347 struct romfs_inode ri;
348 const char *name; /* got from dentry */
349 int len;
350
351 res = -EACCES; /* placeholder for "no data here" */
352 offset = dir->i_ino & ROMFH_MASK;
353 lock_kernel();
354 if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
355 goto error;
356
357 maxoff = romfs_maxsize(dir->i_sb);
358 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
359
360 /* OK, now find the file whose name is in "dentry" in the
361 * directory specified by "dir". */
362
363 name = dentry->d_name.name;
364 len = dentry->d_name.len;
365
366 for(;;) {
367 if (!offset || offset >= maxoff)
368 goto success; /* negative success */
369 if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
370 goto error;
371
372 /* try to match the first 16 bytes of name */
373 fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, ROMFH_SIZE);
374 if (len < ROMFH_SIZE) {
375 if (len == fslen) {
376 /* both are shorter, and same size */
377 romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
378 if (strncmp (name, fsname, len) == 0)
379 break;
380 }
381 } else if (fslen >= ROMFH_SIZE) {
382 /* both are longer; XXX optimize max size */
383 fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, sizeof(fsname)-1);
384 if (len == fslen) {
385 romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
386 if (strncmp(name, fsname, len) == 0)
387 break;
388 }
389 }
390 /* next entry */
391 offset = be32_to_cpu(ri.next) & ROMFH_MASK;
392 }
393
394 /* Hard link handling */
395 if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
396 offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
397
398 inode = romfs_iget(dir->i_sb, offset);
399 if (IS_ERR(inode)) {
400 res = PTR_ERR(inode);
401 goto error;
402 }
403
404 success:
405 d_add(dentry, inode);
406 res = 0;
407 error:
408 unlock_kernel();
409 return ERR_PTR(res);
410 }
411
412 /*
413 * Ok, we do readpage, to be able to execute programs. Unfortunately,
414 * we can't use bmap, since we may have looser alignments.
415 */
416
417 static int
romfs_readpage(struct file * file,struct page * page)418 romfs_readpage(struct file *file, struct page * page)
419 {
420 struct inode *inode = page->mapping->host;
421 loff_t offset, size;
422 unsigned long filled;
423 void *buf;
424 int result = -EIO;
425
426 page_cache_get(page);
427 lock_kernel();
428 buf = kmap(page);
429 if (!buf)
430 goto err_out;
431
432 /* 32 bit warning -- but not for us :) */
433 offset = page_offset(page);
434 size = i_size_read(inode);
435 filled = 0;
436 result = 0;
437 if (offset < size) {
438 unsigned long readlen;
439
440 size -= offset;
441 readlen = size > PAGE_SIZE ? PAGE_SIZE : size;
442
443 filled = romfs_copyfrom(inode, buf, ROMFS_I(inode)->i_dataoffset+offset, readlen);
444
445 if (filled != readlen) {
446 SetPageError(page);
447 filled = 0;
448 result = -EIO;
449 }
450 }
451
452 if (filled < PAGE_SIZE)
453 memset(buf + filled, 0, PAGE_SIZE-filled);
454
455 if (!result)
456 SetPageUptodate(page);
457 flush_dcache_page(page);
458
459 unlock_page(page);
460
461 kunmap(page);
462 err_out:
463 page_cache_release(page);
464 unlock_kernel();
465
466 return result;
467 }
468
469 /* Mapping from our types to the kernel */
470
471 static const struct address_space_operations romfs_aops = {
472 .readpage = romfs_readpage
473 };
474
475 static const struct file_operations romfs_dir_operations = {
476 .read = generic_read_dir,
477 .readdir = romfs_readdir,
478 };
479
480 static const struct inode_operations romfs_dir_inode_operations = {
481 .lookup = romfs_lookup,
482 };
483
484 static mode_t romfs_modemap[] =
485 {
486 0, S_IFDIR+0644, S_IFREG+0644, S_IFLNK+0777,
487 S_IFBLK+0600, S_IFCHR+0600, S_IFSOCK+0644, S_IFIFO+0644
488 };
489
490 static struct inode *
romfs_iget(struct super_block * sb,unsigned long ino)491 romfs_iget(struct super_block *sb, unsigned long ino)
492 {
493 int nextfh, ret;
494 struct romfs_inode ri;
495 struct inode *i;
496
497 ino &= ROMFH_MASK;
498 i = iget_locked(sb, ino);
499 if (!i)
500 return ERR_PTR(-ENOMEM);
501 if (!(i->i_state & I_NEW))
502 return i;
503
504 i->i_mode = 0;
505
506 /* Loop for finding the real hard link */
507 for(;;) {
508 if (romfs_copyfrom(i, &ri, ino, ROMFH_SIZE) <= 0) {
509 printk(KERN_ERR "romfs: read error for inode 0x%lx\n",
510 ino);
511 iget_failed(i);
512 return ERR_PTR(-EIO);
513 }
514 /* XXX: do romfs_checksum here too (with name) */
515
516 nextfh = be32_to_cpu(ri.next);
517 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
518 break;
519
520 ino = be32_to_cpu(ri.spec) & ROMFH_MASK;
521 }
522
523 i->i_nlink = 1; /* Hard to decide.. */
524 i->i_size = be32_to_cpu(ri.size);
525 i->i_mtime.tv_sec = i->i_atime.tv_sec = i->i_ctime.tv_sec = 0;
526 i->i_mtime.tv_nsec = i->i_atime.tv_nsec = i->i_ctime.tv_nsec = 0;
527
528 /* Precalculate the data offset */
529 ret = romfs_strnlen(i, ino + ROMFH_SIZE, ROMFS_MAXFN);
530 if (ret >= 0)
531 ino = (ROMFH_SIZE + ret + 1 + ROMFH_PAD) & ROMFH_MASK;
532 else
533 ino = 0;
534
535 ROMFS_I(i)->i_metasize = ino;
536 ROMFS_I(i)->i_dataoffset = ino+(i->i_ino&ROMFH_MASK);
537
538 /* Compute permissions */
539 ino = romfs_modemap[nextfh & ROMFH_TYPE];
540 /* only "normal" files have ops */
541 switch (nextfh & ROMFH_TYPE) {
542 case 1:
543 i->i_size = ROMFS_I(i)->i_metasize;
544 i->i_op = &romfs_dir_inode_operations;
545 i->i_fop = &romfs_dir_operations;
546 if (nextfh & ROMFH_EXEC)
547 ino |= S_IXUGO;
548 i->i_mode = ino;
549 break;
550 case 2:
551 i->i_fop = &generic_ro_fops;
552 i->i_data.a_ops = &romfs_aops;
553 if (nextfh & ROMFH_EXEC)
554 ino |= S_IXUGO;
555 i->i_mode = ino;
556 break;
557 case 3:
558 i->i_op = &page_symlink_inode_operations;
559 i->i_data.a_ops = &romfs_aops;
560 i->i_mode = ino | S_IRWXUGO;
561 break;
562 default:
563 /* depending on MBZ for sock/fifos */
564 nextfh = be32_to_cpu(ri.spec);
565 init_special_inode(i, ino,
566 MKDEV(nextfh>>16,nextfh&0xffff));
567 }
568 unlock_new_inode(i);
569 return i;
570 }
571
572 static struct kmem_cache * romfs_inode_cachep;
573
romfs_alloc_inode(struct super_block * sb)574 static struct inode *romfs_alloc_inode(struct super_block *sb)
575 {
576 struct romfs_inode_info *ei;
577 ei = kmem_cache_alloc(romfs_inode_cachep, GFP_KERNEL);
578 if (!ei)
579 return NULL;
580 return &ei->vfs_inode;
581 }
582
romfs_destroy_inode(struct inode * inode)583 static void romfs_destroy_inode(struct inode *inode)
584 {
585 kmem_cache_free(romfs_inode_cachep, ROMFS_I(inode));
586 }
587
init_once(void * foo)588 static void init_once(void *foo)
589 {
590 struct romfs_inode_info *ei = foo;
591
592 inode_init_once(&ei->vfs_inode);
593 }
594
init_inodecache(void)595 static int init_inodecache(void)
596 {
597 romfs_inode_cachep = kmem_cache_create("romfs_inode_cache",
598 sizeof(struct romfs_inode_info),
599 0, (SLAB_RECLAIM_ACCOUNT|
600 SLAB_MEM_SPREAD),
601 init_once);
602 if (romfs_inode_cachep == NULL)
603 return -ENOMEM;
604 return 0;
605 }
606
destroy_inodecache(void)607 static void destroy_inodecache(void)
608 {
609 kmem_cache_destroy(romfs_inode_cachep);
610 }
611
romfs_remount(struct super_block * sb,int * flags,char * data)612 static int romfs_remount(struct super_block *sb, int *flags, char *data)
613 {
614 *flags |= MS_RDONLY;
615 return 0;
616 }
617
618 static const struct super_operations romfs_ops = {
619 .alloc_inode = romfs_alloc_inode,
620 .destroy_inode = romfs_destroy_inode,
621 .statfs = romfs_statfs,
622 .remount_fs = romfs_remount,
623 };
624
romfs_get_sb(struct file_system_type * fs_type,int flags,const char * dev_name,void * data,struct vfsmount * mnt)625 static int romfs_get_sb(struct file_system_type *fs_type,
626 int flags, const char *dev_name, void *data, struct vfsmount *mnt)
627 {
628 return get_sb_bdev(fs_type, flags, dev_name, data, romfs_fill_super,
629 mnt);
630 }
631
632 static struct file_system_type romfs_fs_type = {
633 .owner = THIS_MODULE,
634 .name = "romfs",
635 .get_sb = romfs_get_sb,
636 .kill_sb = kill_block_super,
637 .fs_flags = FS_REQUIRES_DEV,
638 };
639
init_romfs_fs(void)640 static int __init init_romfs_fs(void)
641 {
642 int err = init_inodecache();
643 if (err)
644 goto out1;
645 err = register_filesystem(&romfs_fs_type);
646 if (err)
647 goto out;
648 return 0;
649 out:
650 destroy_inodecache();
651 out1:
652 return err;
653 }
654
exit_romfs_fs(void)655 static void __exit exit_romfs_fs(void)
656 {
657 unregister_filesystem(&romfs_fs_type);
658 destroy_inodecache();
659 }
660
661 /* Yes, works even as a module... :) */
662
663 module_init(init_romfs_fs)
664 module_exit(exit_romfs_fs)
665 MODULE_LICENSE("GPL");
666