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/buffer_head.h>
24 #include <linux/vfs.h>
25 #include <linux/mutex.h>
26
27 #include <asm/uaccess.h>
28
29 static const struct super_operations cramfs_ops;
30 static const struct inode_operations cramfs_dir_inode_operations;
31 static const struct file_operations cramfs_directory_operations;
32 static const struct address_space_operations cramfs_aops;
33
34 static DEFINE_MUTEX(read_mutex);
35
36
37 /* These two macros may change in future, to provide better st_ino
38 semantics. */
39 #define CRAMINO(x) (((x)->offset && (x)->size)?(x)->offset<<2:1)
40 #define OFFSET(x) ((x)->i_ino)
41
42
cramfs_iget5_test(struct inode * inode,void * opaque)43 static int cramfs_iget5_test(struct inode *inode, void *opaque)
44 {
45 struct cramfs_inode *cramfs_inode = opaque;
46 return inode->i_ino == CRAMINO(cramfs_inode) && inode->i_ino != 1;
47 }
48
cramfs_iget5_set(struct inode * inode,void * opaque)49 static int cramfs_iget5_set(struct inode *inode, void *opaque)
50 {
51 struct cramfs_inode *cramfs_inode = opaque;
52 inode->i_ino = CRAMINO(cramfs_inode);
53 return 0;
54 }
55
get_cramfs_inode(struct super_block * sb,struct cramfs_inode * cramfs_inode)56 static struct inode *get_cramfs_inode(struct super_block *sb,
57 struct cramfs_inode * cramfs_inode)
58 {
59 struct inode *inode = iget5_locked(sb, CRAMINO(cramfs_inode),
60 cramfs_iget5_test, cramfs_iget5_set,
61 cramfs_inode);
62 static struct timespec zerotime;
63
64 if (inode && (inode->i_state & I_NEW)) {
65 inode->i_mode = cramfs_inode->mode;
66 inode->i_uid = cramfs_inode->uid;
67 inode->i_size = cramfs_inode->size;
68 inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
69 inode->i_gid = cramfs_inode->gid;
70 /* Struct copy intentional */
71 inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
72 /* inode->i_nlink is left 1 - arguably wrong for directories,
73 but it's the best we can do without reading the directory
74 contents. 1 yields the right result in GNU find, even
75 without -noleaf option. */
76 if (S_ISREG(inode->i_mode)) {
77 inode->i_fop = &generic_ro_fops;
78 inode->i_data.a_ops = &cramfs_aops;
79 } else if (S_ISDIR(inode->i_mode)) {
80 inode->i_op = &cramfs_dir_inode_operations;
81 inode->i_fop = &cramfs_directory_operations;
82 } else if (S_ISLNK(inode->i_mode)) {
83 inode->i_op = &page_symlink_inode_operations;
84 inode->i_data.a_ops = &cramfs_aops;
85 } else {
86 init_special_inode(inode, inode->i_mode,
87 old_decode_dev(cramfs_inode->size));
88 }
89 unlock_new_inode(inode);
90 }
91 return inode;
92 }
93
cramfs_drop_inode(struct inode * inode)94 static void cramfs_drop_inode(struct inode *inode)
95 {
96 if (inode->i_ino == 1)
97 generic_delete_inode(inode);
98 else
99 generic_drop_inode(inode);
100 }
101
102 /*
103 * We have our own block cache: don't fill up the buffer cache
104 * with the rom-image, because the way the filesystem is set
105 * up the accesses should be fairly regular and cached in the
106 * page cache and dentry tree anyway..
107 *
108 * This also acts as a way to guarantee contiguous areas of up to
109 * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to
110 * worry about end-of-buffer issues even when decompressing a full
111 * page cache.
112 */
113 #define READ_BUFFERS (2)
114 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
115 #define NEXT_BUFFER(_ix) ((_ix) ^ 1)
116
117 /*
118 * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
119 * data that takes up more space than the original and with unlucky
120 * alignment.
121 */
122 #define BLKS_PER_BUF_SHIFT (2)
123 #define BLKS_PER_BUF (1 << BLKS_PER_BUF_SHIFT)
124 #define BUFFER_SIZE (BLKS_PER_BUF*PAGE_CACHE_SIZE)
125
126 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
127 static unsigned buffer_blocknr[READ_BUFFERS];
128 static struct super_block * buffer_dev[READ_BUFFERS];
129 static int next_buffer;
130
131 /*
132 * Returns a pointer to a buffer containing at least LEN bytes of
133 * filesystem starting at byte offset OFFSET into the filesystem.
134 */
cramfs_read(struct super_block * sb,unsigned int offset,unsigned int len)135 static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
136 {
137 struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
138 struct page *pages[BLKS_PER_BUF];
139 unsigned i, blocknr, buffer;
140 unsigned long devsize;
141 char *data;
142
143 if (!len)
144 return NULL;
145 blocknr = offset >> PAGE_CACHE_SHIFT;
146 offset &= PAGE_CACHE_SIZE - 1;
147
148 /* Check if an existing buffer already has the data.. */
149 for (i = 0; i < READ_BUFFERS; i++) {
150 unsigned int blk_offset;
151
152 if (buffer_dev[i] != sb)
153 continue;
154 if (blocknr < buffer_blocknr[i])
155 continue;
156 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT;
157 blk_offset += offset;
158 if (blk_offset + len > BUFFER_SIZE)
159 continue;
160 return read_buffers[i] + blk_offset;
161 }
162
163 devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT;
164
165 /* Ok, read in BLKS_PER_BUF pages completely first. */
166 for (i = 0; i < BLKS_PER_BUF; i++) {
167 struct page *page = NULL;
168
169 if (blocknr + i < devsize) {
170 page = read_mapping_page_async(mapping, blocknr + i,
171 NULL);
172 /* synchronous error? */
173 if (IS_ERR(page))
174 page = NULL;
175 }
176 pages[i] = page;
177 }
178
179 for (i = 0; i < BLKS_PER_BUF; i++) {
180 struct page *page = pages[i];
181 if (page) {
182 wait_on_page_locked(page);
183 if (!PageUptodate(page)) {
184 /* asynchronous error */
185 page_cache_release(page);
186 pages[i] = NULL;
187 }
188 }
189 }
190
191 buffer = next_buffer;
192 next_buffer = NEXT_BUFFER(buffer);
193 buffer_blocknr[buffer] = blocknr;
194 buffer_dev[buffer] = sb;
195
196 data = read_buffers[buffer];
197 for (i = 0; i < BLKS_PER_BUF; i++) {
198 struct page *page = pages[i];
199 if (page) {
200 memcpy(data, kmap(page), PAGE_CACHE_SIZE);
201 kunmap(page);
202 page_cache_release(page);
203 } else
204 memset(data, 0, PAGE_CACHE_SIZE);
205 data += PAGE_CACHE_SIZE;
206 }
207 return read_buffers[buffer] + offset;
208 }
209
cramfs_put_super(struct super_block * sb)210 static void cramfs_put_super(struct super_block *sb)
211 {
212 kfree(sb->s_fs_info);
213 sb->s_fs_info = NULL;
214 }
215
cramfs_remount(struct super_block * sb,int * flags,char * data)216 static int cramfs_remount(struct super_block *sb, int *flags, char *data)
217 {
218 *flags |= MS_RDONLY;
219 return 0;
220 }
221
cramfs_fill_super(struct super_block * sb,void * data,int silent)222 static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
223 {
224 int i;
225 struct cramfs_super super;
226 unsigned long root_offset;
227 struct cramfs_sb_info *sbi;
228 struct inode *root;
229
230 sb->s_flags |= MS_RDONLY;
231
232 sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
233 if (!sbi)
234 return -ENOMEM;
235 sb->s_fs_info = sbi;
236
237 /* Invalidate the read buffers on mount: think disk change.. */
238 mutex_lock(&read_mutex);
239 for (i = 0; i < READ_BUFFERS; i++)
240 buffer_blocknr[i] = -1;
241
242 /* Read the first block and get the superblock from it */
243 memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
244 mutex_unlock(&read_mutex);
245
246 /* Do sanity checks on the superblock */
247 if (super.magic != CRAMFS_MAGIC) {
248 /* check for wrong endianess */
249 if (super.magic == CRAMFS_MAGIC_WEND) {
250 if (!silent)
251 printk(KERN_ERR "cramfs: wrong endianess\n");
252 goto out;
253 }
254
255 /* check at 512 byte offset */
256 mutex_lock(&read_mutex);
257 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
258 mutex_unlock(&read_mutex);
259 if (super.magic != CRAMFS_MAGIC) {
260 if (super.magic == CRAMFS_MAGIC_WEND && !silent)
261 printk(KERN_ERR "cramfs: wrong endianess\n");
262 else if (!silent)
263 printk(KERN_ERR "cramfs: wrong magic\n");
264 goto out;
265 }
266 }
267
268 /* get feature flags first */
269 if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
270 printk(KERN_ERR "cramfs: unsupported filesystem features\n");
271 goto out;
272 }
273
274 /* Check that the root inode is in a sane state */
275 if (!S_ISDIR(super.root.mode)) {
276 printk(KERN_ERR "cramfs: root is not a directory\n");
277 goto out;
278 }
279 root_offset = super.root.offset << 2;
280 if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
281 sbi->size=super.size;
282 sbi->blocks=super.fsid.blocks;
283 sbi->files=super.fsid.files;
284 } else {
285 sbi->size=1<<28;
286 sbi->blocks=0;
287 sbi->files=0;
288 }
289 sbi->magic=super.magic;
290 sbi->flags=super.flags;
291 if (root_offset == 0)
292 printk(KERN_INFO "cramfs: empty filesystem");
293 else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
294 ((root_offset != sizeof(struct cramfs_super)) &&
295 (root_offset != 512 + sizeof(struct cramfs_super))))
296 {
297 printk(KERN_ERR "cramfs: bad root offset %lu\n", root_offset);
298 goto out;
299 }
300
301 /* Set it all up.. */
302 sb->s_op = &cramfs_ops;
303 root = get_cramfs_inode(sb, &super.root);
304 if (!root)
305 goto out;
306 sb->s_root = d_alloc_root(root);
307 if (!sb->s_root) {
308 iput(root);
309 goto out;
310 }
311 return 0;
312 out:
313 kfree(sbi);
314 sb->s_fs_info = NULL;
315 return -EINVAL;
316 }
317
cramfs_statfs(struct dentry * dentry,struct kstatfs * buf)318 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
319 {
320 struct super_block *sb = dentry->d_sb;
321
322 buf->f_type = CRAMFS_MAGIC;
323 buf->f_bsize = PAGE_CACHE_SIZE;
324 buf->f_blocks = CRAMFS_SB(sb)->blocks;
325 buf->f_bfree = 0;
326 buf->f_bavail = 0;
327 buf->f_files = CRAMFS_SB(sb)->files;
328 buf->f_ffree = 0;
329 buf->f_namelen = CRAMFS_MAXPATHLEN;
330 return 0;
331 }
332
333 /*
334 * Read a cramfs directory entry.
335 */
cramfs_readdir(struct file * filp,void * dirent,filldir_t filldir)336 static int cramfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
337 {
338 struct inode *inode = filp->f_path.dentry->d_inode;
339 struct super_block *sb = inode->i_sb;
340 char *buf;
341 unsigned int offset;
342 int copied;
343
344 /* Offset within the thing. */
345 offset = filp->f_pos;
346 if (offset >= inode->i_size)
347 return 0;
348 /* Directory entries are always 4-byte aligned */
349 if (offset & 3)
350 return -EINVAL;
351
352 buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
353 if (!buf)
354 return -ENOMEM;
355
356 copied = 0;
357 while (offset < inode->i_size) {
358 struct cramfs_inode *de;
359 unsigned long nextoffset;
360 char *name;
361 ino_t ino;
362 mode_t mode;
363 int namelen, error;
364
365 mutex_lock(&read_mutex);
366 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
367 name = (char *)(de+1);
368
369 /*
370 * Namelengths on disk are shifted by two
371 * and the name padded out to 4-byte boundaries
372 * with zeroes.
373 */
374 namelen = de->namelen << 2;
375 memcpy(buf, name, namelen);
376 ino = CRAMINO(de);
377 mode = de->mode;
378 mutex_unlock(&read_mutex);
379 nextoffset = offset + sizeof(*de) + namelen;
380 for (;;) {
381 if (!namelen) {
382 kfree(buf);
383 return -EIO;
384 }
385 if (buf[namelen-1])
386 break;
387 namelen--;
388 }
389 error = filldir(dirent, buf, namelen, offset, ino, mode >> 12);
390 if (error)
391 break;
392
393 offset = nextoffset;
394 filp->f_pos = offset;
395 copied++;
396 }
397 kfree(buf);
398 return 0;
399 }
400
401 /*
402 * Lookup and fill in the inode data..
403 */
cramfs_lookup(struct inode * dir,struct dentry * dentry,struct nameidata * nd)404 static struct dentry * cramfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
405 {
406 unsigned int offset = 0;
407 int sorted;
408
409 mutex_lock(&read_mutex);
410 sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
411 while (offset < dir->i_size) {
412 struct cramfs_inode *de;
413 char *name;
414 int namelen, retval;
415
416 de = cramfs_read(dir->i_sb, OFFSET(dir) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
417 name = (char *)(de+1);
418
419 /* Try to take advantage of sorted directories */
420 if (sorted && (dentry->d_name.name[0] < name[0]))
421 break;
422
423 namelen = de->namelen << 2;
424 offset += sizeof(*de) + namelen;
425
426 /* Quick check that the name is roughly the right length */
427 if (((dentry->d_name.len + 3) & ~3) != namelen)
428 continue;
429
430 for (;;) {
431 if (!namelen) {
432 mutex_unlock(&read_mutex);
433 return ERR_PTR(-EIO);
434 }
435 if (name[namelen-1])
436 break;
437 namelen--;
438 }
439 if (namelen != dentry->d_name.len)
440 continue;
441 retval = memcmp(dentry->d_name.name, name, namelen);
442 if (retval > 0)
443 continue;
444 if (!retval) {
445 struct cramfs_inode entry = *de;
446 mutex_unlock(&read_mutex);
447 d_add(dentry, get_cramfs_inode(dir->i_sb, &entry));
448 return NULL;
449 }
450 /* else (retval < 0) */
451 if (sorted)
452 break;
453 }
454 mutex_unlock(&read_mutex);
455 d_add(dentry, NULL);
456 return NULL;
457 }
458
cramfs_readpage(struct file * file,struct page * page)459 static int cramfs_readpage(struct file *file, struct page * page)
460 {
461 struct inode *inode = page->mapping->host;
462 u32 maxblock, bytes_filled;
463 void *pgdata;
464
465 maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
466 bytes_filled = 0;
467 if (page->index < maxblock) {
468 struct super_block *sb = inode->i_sb;
469 u32 blkptr_offset = OFFSET(inode) + page->index*4;
470 u32 start_offset, compr_len;
471
472 start_offset = OFFSET(inode) + maxblock*4;
473 mutex_lock(&read_mutex);
474 if (page->index)
475 start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4, 4);
476 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) - start_offset);
477 mutex_unlock(&read_mutex);
478 pgdata = kmap(page);
479 if (compr_len == 0)
480 ; /* hole */
481 else if (compr_len > (PAGE_CACHE_SIZE << 1))
482 printk(KERN_ERR "cramfs: bad compressed blocksize %u\n", compr_len);
483 else {
484 mutex_lock(&read_mutex);
485 bytes_filled = cramfs_uncompress_block(pgdata,
486 PAGE_CACHE_SIZE,
487 cramfs_read(sb, start_offset, compr_len),
488 compr_len);
489 mutex_unlock(&read_mutex);
490 }
491 } else
492 pgdata = kmap(page);
493 memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
494 kunmap(page);
495 flush_dcache_page(page);
496 SetPageUptodate(page);
497 unlock_page(page);
498 return 0;
499 }
500
501 static const struct address_space_operations cramfs_aops = {
502 .readpage = cramfs_readpage
503 };
504
505 /*
506 * Our operations:
507 */
508
509 /*
510 * A directory can only readdir
511 */
512 static const struct file_operations cramfs_directory_operations = {
513 .llseek = generic_file_llseek,
514 .read = generic_read_dir,
515 .readdir = cramfs_readdir,
516 };
517
518 static const struct inode_operations cramfs_dir_inode_operations = {
519 .lookup = cramfs_lookup,
520 };
521
522 static const struct super_operations cramfs_ops = {
523 .put_super = cramfs_put_super,
524 .remount_fs = cramfs_remount,
525 .statfs = cramfs_statfs,
526 .drop_inode = cramfs_drop_inode,
527 };
528
cramfs_get_sb(struct file_system_type * fs_type,int flags,const char * dev_name,void * data,struct vfsmount * mnt)529 static int cramfs_get_sb(struct file_system_type *fs_type,
530 int flags, const char *dev_name, void *data, struct vfsmount *mnt)
531 {
532 return get_sb_bdev(fs_type, flags, dev_name, data, cramfs_fill_super,
533 mnt);
534 }
535
536 static struct file_system_type cramfs_fs_type = {
537 .owner = THIS_MODULE,
538 .name = "cramfs",
539 .get_sb = cramfs_get_sb,
540 .kill_sb = kill_block_super,
541 .fs_flags = FS_REQUIRES_DEV,
542 };
543
init_cramfs_fs(void)544 static int __init init_cramfs_fs(void)
545 {
546 int rv;
547
548 rv = cramfs_uncompress_init();
549 if (rv < 0)
550 return rv;
551 rv = register_filesystem(&cramfs_fs_type);
552 if (rv < 0)
553 cramfs_uncompress_exit();
554 return rv;
555 }
556
exit_cramfs_fs(void)557 static void __exit exit_cramfs_fs(void)
558 {
559 cramfs_uncompress_exit();
560 unregister_filesystem(&cramfs_fs_type);
561 }
562
563 module_init(init_cramfs_fs)
564 module_exit(exit_cramfs_fs)
565 MODULE_LICENSE("GPL");
566