1 /*
2 * Compressed rom filesystem for Linux.
3 *
4 * Copyright (C) 1999 Linus Torvalds.
5 *
6 * This file is released under the GPL.
7 */
8
9 /*
10 * These are the VFS interfaces to the compressed rom filesystem.
11 * The actual compression is based on zlib, see the other files.
12 */
13
14 #include <linux/module.h>
15 #include <linux/fs.h>
16 #include <linux/pagemap.h>
17 #include <linux/init.h>
18 #include <linux/string.h>
19 #include <linux/blkdev.h>
20 #include <linux/cramfs_fs.h>
21 #include <linux/slab.h>
22 #include <linux/cramfs_fs_sb.h>
23 #include <linux/vfs.h>
24 #include <linux/mutex.h>
25
26 #include <asm/uaccess.h>
27
28 static const struct super_operations cramfs_ops;
29 static const struct inode_operations cramfs_dir_inode_operations;
30 static const struct file_operations cramfs_directory_operations;
31 static const struct address_space_operations cramfs_aops;
32
33 static DEFINE_MUTEX(read_mutex);
34
35
36 /* These macros may change in future, to provide better st_ino semantics. */
37 #define OFFSET(x) ((x)->i_ino)
38
cramino(const struct cramfs_inode * cino,unsigned int offset)39 static unsigned long cramino(const struct cramfs_inode *cino, unsigned int offset)
40 {
41 if (!cino->offset)
42 return offset + 1;
43 if (!cino->size)
44 return offset + 1;
45
46 /*
47 * The file mode test fixes buggy mkcramfs implementations where
48 * cramfs_inode->offset is set to a non zero value for entries
49 * which did not contain data, like devices node and fifos.
50 */
51 switch (cino->mode & S_IFMT) {
52 case S_IFREG:
53 case S_IFDIR:
54 case S_IFLNK:
55 return cino->offset << 2;
56 default:
57 break;
58 }
59 return offset + 1;
60 }
61
get_cramfs_inode(struct super_block * sb,const struct cramfs_inode * cramfs_inode,unsigned int offset)62 static struct inode *get_cramfs_inode(struct super_block *sb,
63 const struct cramfs_inode *cramfs_inode, unsigned int offset)
64 {
65 struct inode *inode;
66 static struct timespec zerotime;
67
68 inode = iget_locked(sb, cramino(cramfs_inode, offset));
69 if (!inode)
70 return ERR_PTR(-ENOMEM);
71 if (!(inode->i_state & I_NEW))
72 return inode;
73
74 switch (cramfs_inode->mode & S_IFMT) {
75 case S_IFREG:
76 inode->i_fop = &generic_ro_fops;
77 inode->i_data.a_ops = &cramfs_aops;
78 break;
79 case S_IFDIR:
80 inode->i_op = &cramfs_dir_inode_operations;
81 inode->i_fop = &cramfs_directory_operations;
82 break;
83 case S_IFLNK:
84 inode->i_op = &page_symlink_inode_operations;
85 inode->i_data.a_ops = &cramfs_aops;
86 break;
87 default:
88 init_special_inode(inode, cramfs_inode->mode,
89 old_decode_dev(cramfs_inode->size));
90 }
91
92 inode->i_mode = cramfs_inode->mode;
93 i_uid_write(inode, cramfs_inode->uid);
94 i_gid_write(inode, cramfs_inode->gid);
95
96 /* if the lower 2 bits are zero, the inode contains data */
97 if (!(inode->i_ino & 3)) {
98 inode->i_size = cramfs_inode->size;
99 inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
100 }
101
102 /* Struct copy intentional */
103 inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
104 /* inode->i_nlink is left 1 - arguably wrong for directories,
105 but it's the best we can do without reading the directory
106 contents. 1 yields the right result in GNU find, even
107 without -noleaf option. */
108
109 unlock_new_inode(inode);
110
111 return inode;
112 }
113
114 /*
115 * We have our own block cache: don't fill up the buffer cache
116 * with the rom-image, because the way the filesystem is set
117 * up the accesses should be fairly regular and cached in the
118 * page cache and dentry tree anyway..
119 *
120 * This also acts as a way to guarantee contiguous areas of up to
121 * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to
122 * worry about end-of-buffer issues even when decompressing a full
123 * page cache.
124 */
125 #define READ_BUFFERS (2)
126 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
127 #define NEXT_BUFFER(_ix) ((_ix) ^ 1)
128
129 /*
130 * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
131 * data that takes up more space than the original and with unlucky
132 * alignment.
133 */
134 #define BLKS_PER_BUF_SHIFT (2)
135 #define BLKS_PER_BUF (1 << BLKS_PER_BUF_SHIFT)
136 #define BUFFER_SIZE (BLKS_PER_BUF*PAGE_CACHE_SIZE)
137
138 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
139 static unsigned buffer_blocknr[READ_BUFFERS];
140 static struct super_block * buffer_dev[READ_BUFFERS];
141 static int next_buffer;
142
143 /*
144 * Returns a pointer to a buffer containing at least LEN bytes of
145 * filesystem starting at byte offset OFFSET into the filesystem.
146 */
cramfs_read(struct super_block * sb,unsigned int offset,unsigned int len)147 static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
148 {
149 struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
150 struct page *pages[BLKS_PER_BUF];
151 unsigned i, blocknr, buffer;
152 unsigned long devsize;
153 char *data;
154
155 if (!len)
156 return NULL;
157 blocknr = offset >> PAGE_CACHE_SHIFT;
158 offset &= PAGE_CACHE_SIZE - 1;
159
160 /* Check if an existing buffer already has the data.. */
161 for (i = 0; i < READ_BUFFERS; i++) {
162 unsigned int blk_offset;
163
164 if (buffer_dev[i] != sb)
165 continue;
166 if (blocknr < buffer_blocknr[i])
167 continue;
168 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT;
169 blk_offset += offset;
170 if (blk_offset + len > BUFFER_SIZE)
171 continue;
172 return read_buffers[i] + blk_offset;
173 }
174
175 devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT;
176
177 /* Ok, read in BLKS_PER_BUF pages completely first. */
178 for (i = 0; i < BLKS_PER_BUF; i++) {
179 struct page *page = NULL;
180
181 if (blocknr + i < devsize) {
182 page = read_mapping_page_async(mapping, blocknr + i,
183 NULL);
184 /* synchronous error? */
185 if (IS_ERR(page))
186 page = NULL;
187 }
188 pages[i] = page;
189 }
190
191 for (i = 0; i < BLKS_PER_BUF; i++) {
192 struct page *page = pages[i];
193 if (page) {
194 wait_on_page_locked(page);
195 if (!PageUptodate(page)) {
196 /* asynchronous error */
197 page_cache_release(page);
198 pages[i] = NULL;
199 }
200 }
201 }
202
203 buffer = next_buffer;
204 next_buffer = NEXT_BUFFER(buffer);
205 buffer_blocknr[buffer] = blocknr;
206 buffer_dev[buffer] = sb;
207
208 data = read_buffers[buffer];
209 for (i = 0; i < BLKS_PER_BUF; i++) {
210 struct page *page = pages[i];
211 if (page) {
212 memcpy(data, kmap(page), PAGE_CACHE_SIZE);
213 kunmap(page);
214 page_cache_release(page);
215 } else
216 memset(data, 0, PAGE_CACHE_SIZE);
217 data += PAGE_CACHE_SIZE;
218 }
219 return read_buffers[buffer] + offset;
220 }
221
cramfs_put_super(struct super_block * sb)222 static void cramfs_put_super(struct super_block *sb)
223 {
224 kfree(sb->s_fs_info);
225 sb->s_fs_info = NULL;
226 }
227
cramfs_remount(struct super_block * sb,int * flags,char * data)228 static int cramfs_remount(struct super_block *sb, int *flags, char *data)
229 {
230 sync_filesystem(sb);
231 *flags |= MS_RDONLY;
232 return 0;
233 }
234
cramfs_fill_super(struct super_block * sb,void * data,int silent)235 static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
236 {
237 int i;
238 struct cramfs_super super;
239 unsigned long root_offset;
240 struct cramfs_sb_info *sbi;
241 struct inode *root;
242
243 sb->s_flags |= MS_RDONLY;
244
245 sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
246 if (!sbi)
247 return -ENOMEM;
248 sb->s_fs_info = sbi;
249
250 /* Invalidate the read buffers on mount: think disk change.. */
251 mutex_lock(&read_mutex);
252 for (i = 0; i < READ_BUFFERS; i++)
253 buffer_blocknr[i] = -1;
254
255 /* Read the first block and get the superblock from it */
256 memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
257 mutex_unlock(&read_mutex);
258
259 /* Do sanity checks on the superblock */
260 if (super.magic != CRAMFS_MAGIC) {
261 /* check for wrong endianness */
262 if (super.magic == CRAMFS_MAGIC_WEND) {
263 if (!silent)
264 printk(KERN_ERR "cramfs: wrong endianness\n");
265 goto out;
266 }
267
268 /* check at 512 byte offset */
269 mutex_lock(&read_mutex);
270 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
271 mutex_unlock(&read_mutex);
272 if (super.magic != CRAMFS_MAGIC) {
273 if (super.magic == CRAMFS_MAGIC_WEND && !silent)
274 printk(KERN_ERR "cramfs: wrong endianness\n");
275 else if (!silent)
276 printk(KERN_ERR "cramfs: wrong magic\n");
277 goto out;
278 }
279 }
280
281 /* get feature flags first */
282 if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
283 printk(KERN_ERR "cramfs: unsupported filesystem features\n");
284 goto out;
285 }
286
287 /* Check that the root inode is in a sane state */
288 if (!S_ISDIR(super.root.mode)) {
289 printk(KERN_ERR "cramfs: root is not a directory\n");
290 goto out;
291 }
292 /* correct strange, hard-coded permissions of mkcramfs */
293 super.root.mode |= (S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH);
294
295 root_offset = super.root.offset << 2;
296 if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
297 sbi->size=super.size;
298 sbi->blocks=super.fsid.blocks;
299 sbi->files=super.fsid.files;
300 } else {
301 sbi->size=1<<28;
302 sbi->blocks=0;
303 sbi->files=0;
304 }
305 sbi->magic=super.magic;
306 sbi->flags=super.flags;
307 if (root_offset == 0)
308 printk(KERN_INFO "cramfs: empty filesystem");
309 else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
310 ((root_offset != sizeof(struct cramfs_super)) &&
311 (root_offset != 512 + sizeof(struct cramfs_super))))
312 {
313 printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
314 goto out;
315 }
316
317 /* Set it all up.. */
318 sb->s_op = &cramfs_ops;
319 root = get_cramfs_inode(sb, &super.root, 0);
320 if (IS_ERR(root))
321 goto out;
322 sb->s_root = d_make_root(root);
323 if (!sb->s_root)
324 goto out;
325 return 0;
326 out:
327 kfree(sbi);
328 sb->s_fs_info = NULL;
329 return -EINVAL;
330 }
331
cramfs_statfs(struct dentry * dentry,struct kstatfs * buf)332 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
333 {
334 struct super_block *sb = dentry->d_sb;
335 u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
336
337 buf->f_type = CRAMFS_MAGIC;
338 buf->f_bsize = PAGE_CACHE_SIZE;
339 buf->f_blocks = CRAMFS_SB(sb)->blocks;
340 buf->f_bfree = 0;
341 buf->f_bavail = 0;
342 buf->f_files = CRAMFS_SB(sb)->files;
343 buf->f_ffree = 0;
344 buf->f_fsid.val[0] = (u32)id;
345 buf->f_fsid.val[1] = (u32)(id >> 32);
346 buf->f_namelen = CRAMFS_MAXPATHLEN;
347 return 0;
348 }
349
350 /*
351 * Read a cramfs directory entry.
352 */
cramfs_readdir(struct file * filp,void * dirent,filldir_t filldir)353 static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
354 {
355 struct inode *inode = file_inode(filp);
356 struct super_block *sb = inode->i_sb;
357 char *buf;
358 unsigned int offset;
359 int copied;
360
361 /* Offset within the thing. */
362 offset = filp->f_pos;
363 if (offset >= inode->i_size)
364 return 0;
365 /* Directory entries are always 4-byte aligned */
366 if (offset & 3)
367 return -EINVAL;
368
369 buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
370 if (!buf)
371 return -ENOMEM;
372
373 copied = 0;
374 while (offset < inode->i_size) {
375 struct cramfs_inode *de;
376 unsigned long nextoffset;
377 char *name;
378 ino_t ino;
379 umode_t mode;
380 int namelen, error;
381
382 mutex_lock(&read_mutex);
383 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
384 name = (char *)(de+1);
385
386 /*
387 * Namelengths on disk are shifted by two
388 * and the name padded out to 4-byte boundaries
389 * with zeroes.
390 */
391 namelen = de->namelen << 2;
392 memcpy(buf, name, namelen);
393 ino = cramino(de, OFFSET(inode) + offset);
394 mode = de->mode;
395 mutex_unlock(&read_mutex);
396 nextoffset = offset + sizeof(*de) + namelen;
397 for (;;) {
398 if (!namelen) {
399 kfree(buf);
400 return -EIO;
401 }
402 if (buf[namelen-1])
403 break;
404 namelen--;
405 }
406 error = filldir(dirent, buf, namelen, offset, ino, mode >> 12);
407 if (error)
408 break;
409
410 offset = nextoffset;
411 filp->f_pos = offset;
412 copied++;
413 }
414 kfree(buf);
415 return 0;
416 }
417
418 /*
419 * Lookup and fill in the inode data..
420 */
cramfs_lookup(struct inode * dir,struct dentry * dentry,unsigned int flags)421 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
422 {
423 unsigned int offset = 0;
424 struct inode *inode = NULL;
425 int sorted;
426
427 mutex_lock(&read_mutex);
428 sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
429 while (offset < dir->i_size) {
430 struct cramfs_inode *de;
431 char *name;
432 int namelen, retval;
433 int dir_off = OFFSET(dir) + offset;
434
435 de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN);
436 name = (char *)(de+1);
437
438 /* Try to take advantage of sorted directories */
439 if (sorted && (dentry->d_name.name[0] < name[0]))
440 break;
441
442 namelen = de->namelen << 2;
443 offset += sizeof(*de) + namelen;
444
445 /* Quick check that the name is roughly the right length */
446 if (((dentry->d_name.len + 3) & ~3) != namelen)
447 continue;
448
449 for (;;) {
450 if (!namelen) {
451 inode = ERR_PTR(-EIO);
452 goto out;
453 }
454 if (name[namelen-1])
455 break;
456 namelen--;
457 }
458 if (namelen != dentry->d_name.len)
459 continue;
460 retval = memcmp(dentry->d_name.name, name, namelen);
461 if (retval > 0)
462 continue;
463 if (!retval) {
464 inode = get_cramfs_inode(dir->i_sb, de, dir_off);
465 break;
466 }
467 /* else (retval < 0) */
468 if (sorted)
469 break;
470 }
471 out:
472 mutex_unlock(&read_mutex);
473 if (IS_ERR(inode))
474 return ERR_CAST(inode);
475 d_add(dentry, inode);
476 return NULL;
477 }
478
cramfs_readpage(struct file * file,struct page * page)479 static int cramfs_readpage(struct file *file, struct page * page)
480 {
481 struct inode *inode = page->mapping->host;
482 u32 maxblock;
483 int bytes_filled;
484 void *pgdata;
485
486 maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
487 bytes_filled = 0;
488 pgdata = kmap(page);
489
490 if (page->index < maxblock) {
491 struct super_block *sb = inode->i_sb;
492 u32 blkptr_offset = OFFSET(inode) + page->index*4;
493 u32 start_offset, compr_len;
494
495 start_offset = OFFSET(inode) + maxblock*4;
496 mutex_lock(&read_mutex);
497 if (page->index)
498 start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4,
499 4);
500 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) -
501 start_offset);
502 mutex_unlock(&read_mutex);
503
504 if (compr_len == 0)
505 ; /* hole */
506 else if (unlikely(compr_len > (PAGE_CACHE_SIZE << 1))) {
507 pr_err("cramfs: bad compressed blocksize %u\n",
508 compr_len);
509 goto err;
510 } else {
511 mutex_lock(&read_mutex);
512 bytes_filled = cramfs_uncompress_block(pgdata,
513 PAGE_CACHE_SIZE,
514 cramfs_read(sb, start_offset, compr_len),
515 compr_len);
516 mutex_unlock(&read_mutex);
517 if (unlikely(bytes_filled < 0))
518 goto err;
519 }
520 }
521
522 memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
523 flush_dcache_page(page);
524 kunmap(page);
525 SetPageUptodate(page);
526 unlock_page(page);
527 return 0;
528
529 err:
530 kunmap(page);
531 ClearPageUptodate(page);
532 SetPageError(page);
533 unlock_page(page);
534 return 0;
535 }
536
537 static const struct address_space_operations cramfs_aops = {
538 .readpage = cramfs_readpage
539 };
540
541 /*
542 * Our operations:
543 */
544
545 /*
546 * A directory can only readdir
547 */
548 static const struct file_operations cramfs_directory_operations = {
549 .llseek = generic_file_llseek,
550 .read = generic_read_dir,
551 .readdir = cramfs_readdir,
552 };
553
554 static const struct inode_operations cramfs_dir_inode_operations = {
555 .lookup = cramfs_lookup,
556 };
557
558 static const struct super_operations cramfs_ops = {
559 .put_super = cramfs_put_super,
560 .remount_fs = cramfs_remount,
561 .statfs = cramfs_statfs,
562 };
563
cramfs_mount(struct file_system_type * fs_type,int flags,const char * dev_name,void * data)564 static struct dentry *cramfs_mount(struct file_system_type *fs_type,
565 int flags, const char *dev_name, void *data)
566 {
567 return mount_bdev(fs_type, flags, dev_name, data, cramfs_fill_super);
568 }
569
570 static struct file_system_type cramfs_fs_type = {
571 .owner = THIS_MODULE,
572 .name = "cramfs",
573 .mount = cramfs_mount,
574 .kill_sb = kill_block_super,
575 .fs_flags = FS_REQUIRES_DEV,
576 };
577 MODULE_ALIAS_FS("cramfs");
578
init_cramfs_fs(void)579 static int __init init_cramfs_fs(void)
580 {
581 int rv;
582
583 rv = cramfs_uncompress_init();
584 if (rv < 0)
585 return rv;
586 rv = register_filesystem(&cramfs_fs_type);
587 if (rv < 0)
588 cramfs_uncompress_exit();
589 return rv;
590 }
591
exit_cramfs_fs(void)592 static void __exit exit_cramfs_fs(void)
593 {
594 cramfs_uncompress_exit();
595 unregister_filesystem(&cramfs_fs_type);
596 }
597
598 module_init(init_cramfs_fs)
599 module_exit(exit_cramfs_fs)
600 MODULE_LICENSE("GPL");
601