File: /usr/src/linux/fs/romfs/inode.c
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/locks.h>
74 #include <linux/init.h>
75 #include <linux/smp_lock.h>
76
77 #include <asm/uaccess.h>
78
79 static __s32
80 romfs_checksum(void *data, int size)
81 {
82 __s32 sum, *ptr;
83
84 sum = 0; ptr = data;
85 size>>=2;
86 while (size>0) {
87 sum += ntohl(*ptr++);
88 size--;
89 }
90 return sum;
91 }
92
93 static struct super_operations romfs_ops;
94
95 static struct super_block *
96 romfs_read_super(struct super_block *s, void *data, int silent)
97 {
98 struct buffer_head *bh;
99 kdev_t dev = s->s_dev;
100 struct romfs_super_block *rsb;
101 int sz;
102
103 /* I would parse the options here, but there are none.. :) */
104
105 set_blocksize(dev, ROMBSIZE);
106 s->s_blocksize = ROMBSIZE;
107 s->s_blocksize_bits = ROMBSBITS;
108 s->u.generic_sbp = (void *) 0;
109 s->s_maxbytes = 0xFFFFFFFF;
110
111 bh = bread(dev, 0, ROMBSIZE);
112 if (!bh) {
113 /* XXX merge with other printk? */
114 printk ("romfs: unable to read superblock\n");
115 goto outnobh;
116 }
117
118 rsb = (struct romfs_super_block *)bh->b_data;
119 sz = ntohl(rsb->size);
120 if (rsb->word0 != ROMSB_WORD0 || rsb->word1 != ROMSB_WORD1
121 || sz < ROMFH_SIZE) {
122 if (!silent)
123 printk ("VFS: Can't find a romfs filesystem on dev "
124 "%s.\n", kdevname(dev));
125 goto out;
126 }
127 if (romfs_checksum(rsb, min_t(int, sz, 512))) {
128 printk ("romfs: bad initial checksum on dev "
129 "%s.\n", kdevname(dev));
130 goto out;
131 }
132
133 s->s_magic = ROMFS_MAGIC;
134 s->u.romfs_sb.s_maxsize = sz;
135
136 s->s_flags |= MS_RDONLY;
137
138 /* Find the start of the fs */
139 sz = (ROMFH_SIZE +
140 strnlen(rsb->name, ROMFS_MAXFN) + 1 + ROMFH_PAD)
141 & ROMFH_MASK;
142
143 brelse(bh);
144
145 s->s_op = &romfs_ops;
146 s->s_root = d_alloc_root(iget(s, sz));
147
148 if (!s->s_root)
149 goto outnobh;
150
151 /* Ehrhm; sorry.. :) And thanks to Hans-Joachim Widmaier :) */
152 if (0) {
153 out:
154 brelse(bh);
155 outnobh:
156 s = NULL;
157 }
158
159 return s;
160 }
161
162 /* That's simple too. */
163
164 static int
165 romfs_statfs(struct super_block *sb, struct statfs *buf)
166 {
167 buf->f_type = ROMFS_MAGIC;
168 buf->f_bsize = ROMBSIZE;
169 buf->f_bfree = buf->f_bavail = buf->f_ffree;
170 buf->f_blocks = (sb->u.romfs_sb.s_maxsize+ROMBSIZE-1)>>ROMBSBITS;
171 buf->f_namelen = ROMFS_MAXFN;
172 return 0;
173 }
174
175 /* some helper routines */
176
177 static int
178 romfs_strnlen(struct inode *i, unsigned long offset, unsigned long count)
179 {
180 struct buffer_head *bh;
181 unsigned long avail, maxsize, res;
182
183 maxsize = i->i_sb->u.romfs_sb.s_maxsize;
184 if (offset >= maxsize)
185 return -1;
186
187 /* strnlen is almost always valid */
188 if (count > maxsize || offset+count > maxsize)
189 count = maxsize-offset;
190
191 bh = bread(i->i_dev, offset>>ROMBSBITS, ROMBSIZE);
192 if (!bh)
193 return -1; /* error */
194
195 avail = ROMBSIZE - (offset & ROMBMASK);
196 maxsize = min_t(unsigned long, count, avail);
197 res = strnlen(((char *)bh->b_data)+(offset&ROMBMASK), maxsize);
198 brelse(bh);
199
200 if (res < maxsize)
201 return res; /* found all of it */
202
203 while (res < count) {
204 offset += maxsize;
205
206 bh = bread(i->i_dev, offset>>ROMBSBITS, ROMBSIZE);
207 if (!bh)
208 return -1;
209 maxsize = min_t(unsigned long, count - res, ROMBSIZE);
210 avail = strnlen(bh->b_data, maxsize);
211 res += avail;
212 brelse(bh);
213 if (avail < maxsize)
214 return res;
215 }
216 return res;
217 }
218
219 static int
220 romfs_copyfrom(struct inode *i, void *dest, unsigned long offset, unsigned long count)
221 {
222 struct buffer_head *bh;
223 unsigned long avail, maxsize, res;
224
225 maxsize = i->i_sb->u.romfs_sb.s_maxsize;
226 if (offset >= maxsize || count > maxsize || offset+count>maxsize)
227 return -1;
228
229 bh = bread(i->i_dev, offset>>ROMBSBITS, ROMBSIZE);
230 if (!bh)
231 return -1; /* error */
232
233 avail = ROMBSIZE - (offset & ROMBMASK);
234 maxsize = min_t(unsigned long, count, avail);
235 memcpy(dest, ((char *)bh->b_data) + (offset & ROMBMASK), maxsize);
236 brelse(bh);
237
238 res = maxsize; /* all of it */
239
240 while (res < count) {
241 offset += maxsize;
242 dest += maxsize;
243
244 bh = bread(i->i_dev, offset>>ROMBSBITS, ROMBSIZE);
245 if (!bh)
246 return -1;
247 maxsize = min_t(unsigned long, count - res, ROMBSIZE);
248 memcpy(dest, bh->b_data, maxsize);
249 brelse(bh);
250 res += maxsize;
251 }
252 return res;
253 }
254
255 static unsigned char romfs_dtype_table[] = {
256 DT_UNKNOWN, DT_DIR, DT_REG, DT_LNK, DT_BLK, DT_CHR, DT_SOCK, DT_FIFO
257 };
258
259 static int
260 romfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
261 {
262 struct inode *i = filp->f_dentry->d_inode;
263 struct romfs_inode ri;
264 unsigned long offset, maxoff;
265 int j, ino, nextfh;
266 int stored = 0;
267 char fsname[ROMFS_MAXFN]; /* XXX dynamic? */
268
269 maxoff = i->i_sb->u.romfs_sb.s_maxsize;
270
271 offset = filp->f_pos;
272 if (!offset) {
273 offset = i->i_ino & ROMFH_MASK;
274 if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 0)
275 return stored;
276 offset = ntohl(ri.spec) & ROMFH_MASK;
277 }
278
279 /* Not really failsafe, but we are read-only... */
280 for(;;) {
281 if (!offset || offset >= maxoff) {
282 offset = maxoff;
283 filp->f_pos = offset;
284 return stored;
285 }
286 filp->f_pos = offset;
287
288 /* Fetch inode info */
289 if (romfs_copyfrom(i, &ri, offset, ROMFH_SIZE) <= 0)
290 return stored;
291
292 j = romfs_strnlen(i, offset+ROMFH_SIZE, sizeof(fsname)-1);
293 if (j < 0)
294 return stored;
295
296 fsname[j]=0;
297 romfs_copyfrom(i, fsname, offset+ROMFH_SIZE, j);
298
299 ino = offset;
300 nextfh = ntohl(ri.next);
301 if ((nextfh & ROMFH_TYPE) == ROMFH_HRD)
302 ino = ntohl(ri.spec);
303 if (filldir(dirent, fsname, j, offset, ino,
304 romfs_dtype_table[nextfh & ROMFH_TYPE]) < 0) {
305 return stored;
306 }
307 stored++;
308 offset = nextfh & ROMFH_MASK;
309 }
310 }
311
312 static struct dentry *
313 romfs_lookup(struct inode *dir, struct dentry *dentry)
314 {
315 unsigned long offset, maxoff;
316 int fslen, res;
317 struct inode *inode;
318 char fsname[ROMFS_MAXFN]; /* XXX dynamic? */
319 struct romfs_inode ri;
320 const char *name; /* got from dentry */
321 int len;
322
323 res = -EACCES; /* placeholder for "no data here" */
324 offset = dir->i_ino & ROMFH_MASK;
325 if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
326 goto out;
327
328 maxoff = dir->i_sb->u.romfs_sb.s_maxsize;
329 offset = ntohl(ri.spec) & ROMFH_MASK;
330
331 /* OK, now find the file whose name is in "dentry" in the
332 * directory specified by "dir". */
333
334 name = dentry->d_name.name;
335 len = dentry->d_name.len;
336
337 for(;;) {
338 if (!offset || offset >= maxoff)
339 goto out0;
340 if (romfs_copyfrom(dir, &ri, offset, ROMFH_SIZE) <= 0)
341 goto out;
342
343 /* try to match the first 16 bytes of name */
344 fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, ROMFH_SIZE);
345 if (len < ROMFH_SIZE) {
346 if (len == fslen) {
347 /* both are shorter, and same size */
348 romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
349 if (strncmp (name, fsname, len) == 0)
350 break;
351 }
352 } else if (fslen >= ROMFH_SIZE) {
353 /* both are longer; XXX optimize max size */
354 fslen = romfs_strnlen(dir, offset+ROMFH_SIZE, sizeof(fsname)-1);
355 if (len == fslen) {
356 romfs_copyfrom(dir, fsname, offset+ROMFH_SIZE, len+1);
357 if (strncmp(name, fsname, len) == 0)
358 break;
359 }
360 }
361 /* next entry */
362 offset = ntohl(ri.next) & ROMFH_MASK;
363 }
364
365 /* Hard link handling */
366 if ((ntohl(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
367 offset = ntohl(ri.spec) & ROMFH_MASK;
368
369 if ((inode = iget(dir->i_sb, offset)))
370 goto outi;
371
372 /*
373 * it's a bit funky, _lookup needs to return an error code
374 * (negative) or a NULL, both as a dentry. ENOENT should not
375 * be returned, instead we need to create a negative dentry by
376 * d_add(dentry, NULL); and return 0 as no error.
377 * (Although as I see, it only matters on writable file
378 * systems).
379 */
380
381 out0: inode = NULL;
382 outi: res = 0;
383 d_add (dentry, inode);
384
385 out: return ERR_PTR(res);
386 }
387
388 /*
389 * Ok, we do readpage, to be able to execute programs. Unfortunately,
390 * we can't use bmap, since we may have looser alignments.
391 */
392
393 static int
394 romfs_readpage(struct file *file, struct page * page)
395 {
396 struct inode *inode = page->mapping->host;
397 unsigned long offset, avail, readlen;
398 void *buf;
399 int result = -EIO;
400
401 page_cache_get(page);
402 lock_kernel();
403 buf = kmap(page);
404 if (!buf)
405 goto err_out;
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_t(unsigned long, 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 kunmap(page);
429 err_out:
430 page_cache_release(page);
431 unlock_kernel();
432
433 return result;
434 }
435
436 /* Mapping from our types to the kernel */
437
438 static struct address_space_operations romfs_aops = {
439 readpage: romfs_readpage
440 };
441
442 static struct file_operations romfs_dir_operations = {
443 read: generic_read_dir,
444 readdir: romfs_readdir,
445 };
446
447 static struct inode_operations romfs_dir_inode_operations = {
448 lookup: romfs_lookup,
449 };
450
451 static mode_t romfs_modemap[] =
452 {
453 0, S_IFDIR+0644, S_IFREG+0644, S_IFLNK+0777,
454 S_IFBLK+0600, S_IFCHR+0600, S_IFSOCK+0644, S_IFIFO+0644
455 };
456
457 static void
458 romfs_read_inode(struct inode *i)
459 {
460 int nextfh, ino;
461 struct romfs_inode ri;
462
463 ino = i->i_ino & ROMFH_MASK;
464 i->i_mode = 0;
465
466 /* Loop for finding the real hard link */
467 for(;;) {
468 if (romfs_copyfrom(i, &ri, ino, ROMFH_SIZE) <= 0) {
469 printk("romfs: read error for inode 0x%x\n", ino);
470 return;
471 }
472 /* XXX: do romfs_checksum here too (with name) */
473
474 nextfh = ntohl(ri.next);
475 if ((nextfh & ROMFH_TYPE) != ROMFH_HRD)
476 break;
477
478 ino = ntohl(ri.spec) & ROMFH_MASK;
479 }
480
481 i->i_nlink = 1; /* Hard to decide.. */
482 i->i_size = ntohl(ri.size);
483 i->i_mtime = i->i_atime = i->i_ctime = 0;
484 i->i_uid = i->i_gid = 0;
485
486 /* Precalculate the data offset */
487 ino = romfs_strnlen(i, ino+ROMFH_SIZE, ROMFS_MAXFN);
488 if (ino >= 0)
489 ino = ((ROMFH_SIZE+ino+1+ROMFH_PAD)&ROMFH_MASK);
490 else
491 ino = 0;
492
493 i->u.romfs_i.i_metasize = ino;
494 i->u.romfs_i.i_dataoffset = ino+(i->i_ino&ROMFH_MASK);
495
496 /* Compute permissions */
497 ino = romfs_modemap[nextfh & ROMFH_TYPE];
498 /* only "normal" files have ops */
499 switch (nextfh & ROMFH_TYPE) {
500 case 1:
501 i->i_size = i->u.romfs_i.i_metasize;
502 i->i_op = &romfs_dir_inode_operations;
503 i->i_fop = &romfs_dir_operations;
504 if (nextfh & ROMFH_EXEC)
505 ino |= S_IXUGO;
506 i->i_mode = ino;
507 break;
508 case 2:
509 i->i_fop = &generic_ro_fops;
510 i->i_data.a_ops = &romfs_aops;
511 if (nextfh & ROMFH_EXEC)
512 ino |= S_IXUGO;
513 i->i_mode = ino;
514 break;
515 case 3:
516 i->i_op = &page_symlink_inode_operations;
517 i->i_data.a_ops = &romfs_aops;
518 i->i_mode = ino | S_IRWXUGO;
519 break;
520 default:
521 /* depending on MBZ for sock/fifos */
522 nextfh = ntohl(ri.spec);
523 nextfh = kdev_t_to_nr(MKDEV(nextfh>>16,nextfh&0xffff));
524 init_special_inode(i, ino, nextfh);
525 }
526 }
527
528 static struct super_operations romfs_ops = {
529 read_inode: romfs_read_inode,
530 statfs: romfs_statfs,
531 };
532
533 static DECLARE_FSTYPE_DEV(romfs_fs_type, "romfs", romfs_read_super);
534
535 static int __init init_romfs_fs(void)
536 {
537 return register_filesystem(&romfs_fs_type);
538 }
539
540 static void __exit exit_romfs_fs(void)
541 {
542 unregister_filesystem(&romfs_fs_type);
543 }
544
545 /* Yes, works even as a module... :) */
546
547 EXPORT_NO_SYMBOLS;
548
549 module_init(init_romfs_fs)
550 module_exit(exit_romfs_fs)
551