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/malloc.h>
71 #include <linux/romfs_fs.h>
72 #include <linux/fs.h>
73 #include <linux/locks.h>
74 #include <linux/init.h>
75 #include <linux/smp_lock.h>
76
77 #include <asm/uaccess.h>
78
79 static int inline min(int a, int b)
80 {
81 return a<b ? a : b;
82 }
83
84 static __s32
85 romfs_checksum(void *data, int size)
86 {
87 __s32 sum, *ptr;
88
89 sum = 0; ptr = data;
90 size>>=2;
91 while (size>0) {
92 sum += ntohl(*ptr++);
93 size--;
94 }
95 return sum;
96 }
97
98 static struct super_operations romfs_ops;
99
100 static struct super_block *
101 romfs_read_super(struct super_block *s, void *data, int silent)
102 {
103 struct buffer_head *bh;
104 kdev_t dev = s->s_dev;
105 struct romfs_super_block *rsb;
106 int sz;
107
108 /* I would parse the options here, but there are none.. :) */
109
110 set_blocksize(dev, ROMBSIZE);
111 s->s_blocksize = ROMBSIZE;
112 s->s_blocksize_bits = ROMBSBITS;
113 bh = bread(dev, 0, ROMBSIZE);
114 if (!bh) {
115 /* XXX merge with other printk? */
116 printk ("romfs: unable to read superblock\n");
117 goto outnobh;
118 }
119
120 rsb = (struct romfs_super_block *)bh->b_data;
121 sz = ntohl(rsb->size);
122 if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1
123 || sz < ROMFH_SIZE) {
124 if (!silent)
125 printk ("VFS: Can't find a romfs filesystem on dev "
126 "%s.\n", kdevname(dev));
127 goto out;
128 }
129 if (romfs_checksum(rsb, min(sz,512))) {
130 printk ("romfs: bad initial checksum on dev "
131 "%s.\n", kdevname(dev));
132 goto out;
133 }
134
135 s->s_magic = ROMFS_MAGIC;
136 s->u.romfs_sb.s_maxsize = sz;
137
138 s->s_flags |= MS_RDONLY;
139
140 /* Find the start of the fs */
141 sz = (ROMFH_SIZE +
142 strnlen(rsb->name, ROMFS_MAXFN) + 1 + ROMFH_PAD)
143 & ROMFH_MASK;
144
145 brelse(bh);
146
147 s->s_op = &romfs_ops;
148 s->s_root = d_alloc_root(iget(s, sz));
149
150 if (!s->s_root)
151 goto outnobh;
152
153 /* Ehrhm; sorry.. :) And thanks to Hans-Joachim Widmaier :) */
154 if (0) {
155 out:
156 brelse(bh);
157 outnobh:
158 s = NULL;
159 }
160
161 return s;
162 }
163
164 /* That's simple too. */
165
166 static int
167 romfs_statfs(struct super_block *sb, struct statfs *buf)
168 {
169 buf->f_type = ROMFS_MAGIC;
170 buf->f_bsize = ROMBSIZE;
171 buf->f_bfree = buf->f_bavail = buf->f_ffree;
172 buf->f_blocks = (sb->u.romfs_sb.s_maxsize+ROMBSIZE-1)>>ROMBSBITS;
173 buf->f_namelen = ROMFS_MAXFN;
174 return 0;
175 }
176
177 /* some helper routines */
178
179 static int
180 romfs_strnlen(struct inode *i, unsigned long offset, unsigned long count)
181 {
182 struct buffer_head *bh;
183 unsigned long avail, maxsize, res;
184
185 maxsize = i->i_sb->u.romfs_sb.s_maxsize;
186 if (offset >= maxsize)
187 return -1;
188
189 /* strnlen is almost always valid */
190 if (count > maxsize || offset+count > maxsize)
191 count = maxsize-offset;
192
193 bh = bread(i->i_dev, offset>>ROMBSBITS, ROMBSIZE);
194 if (!bh)
195 return -1; /* error */
196
197 avail = ROMBSIZE - (offset & ROMBMASK);
198 maxsize = min(count, avail);
199 res = strnlen(((char *)bh->b_data)+(offset&ROMBMASK), maxsize);
200 brelse(bh);
201
202 if (res < maxsize)
203 return res; /* found all of it */
204
205 while (res < count) {
206 offset += maxsize;
207
208 bh = bread(i->i_dev, offset>>ROMBSBITS, ROMBSIZE);
209 if (!bh)
210 return -1;
211 maxsize = min(count-res, ROMBSIZE);
212 avail = strnlen(bh->b_data, maxsize);
213 res += avail;
214 brelse(bh);
215 if (avail < maxsize)
216 return res;
217 }
218 return res;
219 }
220
221 static int
222 romfs_copyfrom(struct inode *i, void *dest, unsigned long offset, unsigned long count)
223 {
224 struct buffer_head *bh;
225 unsigned long avail, maxsize, res;
226
227 maxsize = i->i_sb->u.romfs_sb.s_maxsize;
228 if (offset >= maxsize || count > maxsize || offset+count>maxsize)
229 return -1;
230
231 bh = bread(i->i_dev, offset>>ROMBSBITS, ROMBSIZE);
232 if (!bh)
233 return -1; /* error */
234
235 avail = ROMBSIZE - (offset & ROMBMASK);
236 maxsize = min(count, avail);
237 memcpy(dest, ((char *)bh->b_data) + (offset & ROMBMASK), maxsize);
238 brelse(bh);
239
240 res = maxsize; /* all of it */
241
242 while (res < count) {
243 offset += maxsize;
244 dest += maxsize;
245
246 bh = bread(i->i_dev, offset>>ROMBSBITS, ROMBSIZE);
247 if (!bh)
248 return -1;
249 maxsize = min(count-res, ROMBSIZE);
250 memcpy(dest, bh->b_data, maxsize);
251 brelse(bh);
252 res += maxsize;
253 }
254 return res;
255 }
256
257 static unsigned char romfs_dtype_table[] = {
258 DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
259 };
260
261 static int
262 romfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
263 {
264 struct inode *i = filp->f_dentry->d_inode;
265 struct romfs_inode ri;
266 unsigned long offset, maxoff;
267 int j, ino, nextfh;
268 int stored = 0;
269 char fsname[ROMFS_MAXFN]; /* XXX dynamic? */
270
271 maxoff = i->i_sb->u.romfs_sb.s_maxsize;
272
273 offset = filp->f_pos;
274 if (!offset) {
275 offset = i->i_ino & ROMFH_MASK;
276 if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 0)
277 return stored;
278 offset = ntohl(ri.spec) & ROMFH_MASK;
279 }
280
281 /* Not really failsafe, but we are read-only... */
282 for(;;) {
283 if (!offset || offset >= maxoff) {
284 offset = maxoff;
285 filp->f_pos = offset;
286 return stored;
287 }
288 filp->f_pos = offset;
289
290 /* Fetch inode info */
291 if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 0)
292 return stored;
293
294 j = romfs_strnlen(i, offset+ROMFH_SIZE, sizeof(fsname)-1);
295 if (j < 0)
296 return stored;
297
298 fsname[j]=0;
299 romfs_copyfrom(i, fsname, offset+ROMFH_SIZE, j);
300
301 ino = offset;
302 nextfh = ntohl(ri.next);
303 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
304 ino = ntohl(ri.spec);
305 if (filldir(dirent, fsname, j, offset, ino,
306 romfs_dtype_table[nextfh & ROMFH_TYPE]) < 0) {
307 return stored;
308 }
309 stored++;
310 offset = nextfh & ROMFH_MASK;
311 }
312 }
313
314 static struct dentry *
315 romfs_lookup(struct inode *dir, struct dentry *dentry)
316 {
317 unsigned long offset, maxoff;
318 int fslen, res;
319 struct inode *inode;
320 char fsname[ROMFS_MAXFN]; /* XXX dynamic? */
321 struct romfs_inode ri;
322 const char *name; /* got from dentry */
323 int len;
324
325 res = -EACCES; /* placeholder for "no data here" */
326 offset = dir->i_ino & ROMFH_MASK;
327 if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
328 goto out;
329
330 maxoff = dir->i_sb->u.romfs_sb.s_maxsize;
331 offset = ntohl(ri.spec) & ROMFH_MASK;
332
333 /* OK, now find the file whose name is in "dentry" in the
334 * directory specified by "dir". */
335
336 name = dentry->d_name.name;
337 len = dentry->d_name.len;
338
339 for(;;) {
340 if (!offset || offset >= maxoff)
341 goto out0;
342 if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
343 goto out;
344
345 /* try to match the first 16 bytes of name */
346 fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, ROMFH_SIZE);
347 if (len < ROMFH_SIZE) {
348 if (len == fslen) {
349 /* both are shorter, and same size */
350 romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
351 if (strncmp (name, fsname, len) == 0)
352 break;
353 }
354 } else if (fslen >= ROMFH_SIZE) {
355 /* both are longer; XXX optimize max size */
356 fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, sizeof(fsname)-1);
357 if (len == fslen) {
358 romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
359 if (strncmp(name, fsname, len) == 0)
360 break;
361 }
362 }
363 /* next entry */
364 offset = ntohl(ri.next) & ROMFH_MASK;
365 }
366
367 /* Hard link handling */
368 if ((ntohl(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
369 offset = ntohl(ri.spec) & ROMFH_MASK;
370
371 if ((inode = iget(dir->i_sb, offset)))
372 goto outi;
373
374 /*
375 * it's a bit funky, _lookup needs to return an error code
376 * (negative) or a NULL, both as a dentry. ENOENT should not
377 * be returned, instead we need to create a negative dentry by
378 * d_add(dentry, NULL); and return 0 as no error.
379 * (Although as I see, it only matters on writable file
380 * systems).
381 */
382
383 out0: inode = NULL;
384 outi: res = 0;
385 d_add (dentry, inode);
386
387 out: return ERR_PTR(res);
388 }
389
390 /*
391 * Ok, we do readpage, to be able to execute programs. Unfortunately,
392 * we can't use bmap, since we may have looser alignments.
393 */
394
395 static int
396 romfs_readpage(struct file *file, struct page * page)
397 {
398 struct inode *inode = page->mapping->host;
399 unsigned long offset, avail, readlen;
400 void *buf;
401 int result = -EIO;
402
403 lock_kernel();
404 get_page(page);
405 buf = page_address(page);
406
407 /* 32 bit warning -- but not for us :) */
408 offset = page->index << PAGE_CACHE_SHIFT;
409 if (offset < inode->i_size) {
410 avail = inode->i_size-offset;
411 readlen = min(avail, PAGE_SIZE);
412 if (romfs_copyfrom(inode, buf, inode->u.romfs_i.i_dataoffset+offset, readlen) == readlen) {
413 if (readlen < PAGE_SIZE) {
414 memset(buf + readlen,0,PAGE_SIZE-readlen);
415 }
416 SetPageUptodate(page);
417 result = 0;
418 }
419 }
420 if (result) {
421 memset(buf, 0, PAGE_SIZE);
422 SetPageError(page);
423 }
424 flush_dcache_page(page);
425
426 UnlockPage(page);
427
428 __free_page(page);
429 unlock_kernel();
430
431 return result;
432 }
433
434 /* Mapping from our types to the kernel */
435
436 static struct address_space_operations romfs_aops = {
437 readpage: romfs_readpage
438 };
439
440 static struct file_operations romfs_dir_operations = {
441 read: generic_read_dir,
442 readdir: romfs_readdir,
443 };
444
445 static struct inode_operations romfs_dir_inode_operations = {
446 lookup: romfs_lookup,
447 };
448
449 static mode_t romfs_modemap[] =
450 {
451 0, S_IFDIR+0644, S_IFREG+0644, S_IFLNK+0777,
452 S_IFBLK+0600, S_IFCHR+0600, S_IFSOCK+0644, S_IFIFO+0644
453 };
454
455 static void
456 romfs_read_inode(struct inode *i)
457 {
458 int nextfh, ino;
459 struct romfs_inode ri;
460
461 ino = i->i_ino & ROMFH_MASK;
462 i->i_mode = 0;
463
464 /* Loop for finding the real hard link */
465 for(;;) {
466 if (romfs_copyfrom(i, &ri, ino, ROMFH_SIZE) <= 0) {
467 printk("romfs: read error for inode 0x%x\n", ino);
468 return;
469 }
470 /* XXX: do romfs_checksum here too (with name) */
471
472 nextfh = ntohl(ri.next);
473 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
474 break;
475
476 ino = ntohl(ri.spec) & ROMFH_MASK;
477 }
478
479 i->i_nlink = 1; /* Hard to decide.. */
480 i->i_size = ntohl(ri.size);
481 i->i_mtime = i->i_atime = i->i_ctime = 0;
482 i->i_uid = i->i_gid = 0;
483
484 /* Precalculate the data offset */
485 ino = romfs_strnlen(i, ino+ROMFH_SIZE, ROMFS_MAXFN);
486 if (ino >= 0)
487 ino = ((ROMFH_SIZE+ino+1+ROMFH_PAD)&ROMFH_MASK);
488 else
489 ino = 0;
490
491 i->u.romfs_i.i_metasize = ino;
492 i->u.romfs_i.i_dataoffset = ino+(i->i_ino&ROMFH_MASK);
493
494 /* Compute permissions */
495 ino = romfs_modemap[nextfh & ROMFH_TYPE];
496 /* only "normal" files have ops */
497 switch (nextfh & ROMFH_TYPE) {
498 case 1:
499 i->i_size = i->u.romfs_i.i_metasize;
500 i->i_op = &romfs_dir_inode_operations;
501 i->i_fop = &romfs_dir_operations;
502 if (nextfh & ROMFH_EXEC)
503 ino |= S_IXUGO;
504 i->i_mode = ino;
505 break;
506 case 2:
507 i->i_fop = &generic_ro_fops;
508 i->i_data.a_ops = &romfs_aops;
509 if (nextfh & ROMFH_EXEC)
510 ino |= S_IXUGO;
511 i->i_mode = ino;
512 break;
513 case 3:
514 i->i_op = &page_symlink_inode_operations;
515 i->i_data.a_ops = &romfs_aops;
516 i->i_mode = ino | S_IRWXUGO;
517 break;
518 default:
519 /* depending on MBZ for sock/fifos */
520 nextfh = ntohl(ri.spec);
521 nextfh = kdev_t_to_nr(MKDEV(nextfh>>16,nextfh&0xffff));
522 init_special_inode(i, ino, nextfh);
523 }
524 }
525
526 static struct super_operations romfs_ops = {
527 read_inode: romfs_read_inode,
528 statfs: romfs_statfs,
529 };
530
531 static DECLARE_FSTYPE_DEV(romfs_fs_type, "romfs", romfs_read_super);
532
533 static int __init init_romfs_fs(void)
534 {
535 return register_filesystem(&romfs_fs_type);
536 }
537
538 static void __exit exit_romfs_fs(void)
539 {
540 unregister_filesystem(&romfs_fs_type);
541 }
542
543 /* Yes, works even as a module... :) */
544
545 EXPORT_NO_SYMBOLS;
546
547 module_init(init_romfs_fs)
548 module_exit(exit_romfs_fs)
549
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