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TOMOYO Linux Cross Reference
Linux/fs/cramfs/inode.c

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  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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 15 
 16 #include <linux/module.h>
 17 #include <linux/fs.h>
 18 #include <linux/pagemap.h>
 19 #include <linux/init.h>
 20 #include <linux/string.h>
 21 #include <linux/blkdev.h>
 22 #include <linux/slab.h>
 23 #include <linux/vfs.h>
 24 #include <linux/mutex.h>
 25 #include <uapi/linux/cramfs_fs.h>
 26 #include <linux/uaccess.h>
 27 
 28 #include "internal.h"
 29 
 30 /*
 31  * cramfs super-block data in memory
 32  */
 33 struct cramfs_sb_info {
 34         unsigned long magic;
 35         unsigned long size;
 36         unsigned long blocks;
 37         unsigned long files;
 38         unsigned long flags;
 39 };
 40 
 41 static inline struct cramfs_sb_info *CRAMFS_SB(struct super_block *sb)
 42 {
 43         return sb->s_fs_info;
 44 }
 45 
 46 static const struct super_operations cramfs_ops;
 47 static const struct inode_operations cramfs_dir_inode_operations;
 48 static const struct file_operations cramfs_directory_operations;
 49 static const struct address_space_operations cramfs_aops;
 50 
 51 static DEFINE_MUTEX(read_mutex);
 52 
 53 
 54 /* These macros may change in future, to provide better st_ino semantics. */
 55 #define OFFSET(x)       ((x)->i_ino)
 56 
 57 static unsigned long cramino(const struct cramfs_inode *cino, unsigned int offset)
 58 {
 59         if (!cino->offset)
 60                 return offset + 1;
 61         if (!cino->size)
 62                 return offset + 1;
 63 
 64         /*
 65          * The file mode test fixes buggy mkcramfs implementations where
 66          * cramfs_inode->offset is set to a non zero value for entries
 67          * which did not contain data, like devices node and fifos.
 68          */
 69         switch (cino->mode & S_IFMT) {
 70         case S_IFREG:
 71         case S_IFDIR:
 72         case S_IFLNK:
 73                 return cino->offset << 2;
 74         default:
 75                 break;
 76         }
 77         return offset + 1;
 78 }
 79 
 80 static struct inode *get_cramfs_inode(struct super_block *sb,
 81         const struct cramfs_inode *cramfs_inode, unsigned int offset)
 82 {
 83         struct inode *inode;
 84         static struct timespec zerotime;
 85 
 86         inode = iget_locked(sb, cramino(cramfs_inode, offset));
 87         if (!inode)
 88                 return ERR_PTR(-ENOMEM);
 89         if (!(inode->i_state & I_NEW))
 90                 return inode;
 91 
 92         switch (cramfs_inode->mode & S_IFMT) {
 93         case S_IFREG:
 94                 inode->i_fop = &generic_ro_fops;
 95                 inode->i_data.a_ops = &cramfs_aops;
 96                 break;
 97         case S_IFDIR:
 98                 inode->i_op = &cramfs_dir_inode_operations;
 99                 inode->i_fop = &cramfs_directory_operations;
100                 break;
101         case S_IFLNK:
102                 inode->i_op = &page_symlink_inode_operations;
103                 inode->i_data.a_ops = &cramfs_aops;
104                 break;
105         default:
106                 init_special_inode(inode, cramfs_inode->mode,
107                                 old_decode_dev(cramfs_inode->size));
108         }
109 
110         inode->i_mode = cramfs_inode->mode;
111         i_uid_write(inode, cramfs_inode->uid);
112         i_gid_write(inode, cramfs_inode->gid);
113 
114         /* if the lower 2 bits are zero, the inode contains data */
115         if (!(inode->i_ino & 3)) {
116                 inode->i_size = cramfs_inode->size;
117                 inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
118         }
119 
120         /* Struct copy intentional */
121         inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
122         /* inode->i_nlink is left 1 - arguably wrong for directories,
123            but it's the best we can do without reading the directory
124            contents.  1 yields the right result in GNU find, even
125            without -noleaf option. */
126 
127         unlock_new_inode(inode);
128 
129         return inode;
130 }
131 
132 /*
133  * We have our own block cache: don't fill up the buffer cache
134  * with the rom-image, because the way the filesystem is set
135  * up the accesses should be fairly regular and cached in the
136  * page cache and dentry tree anyway..
137  *
138  * This also acts as a way to guarantee contiguous areas of up to
139  * BLKS_PER_BUF*PAGE_CACHE_SIZE, so that the caller doesn't need to
140  * worry about end-of-buffer issues even when decompressing a full
141  * page cache.
142  */
143 #define READ_BUFFERS (2)
144 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
145 #define NEXT_BUFFER(_ix) ((_ix) ^ 1)
146 
147 /*
148  * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
149  * data that takes up more space than the original and with unlucky
150  * alignment.
151  */
152 #define BLKS_PER_BUF_SHIFT      (2)
153 #define BLKS_PER_BUF            (1 << BLKS_PER_BUF_SHIFT)
154 #define BUFFER_SIZE             (BLKS_PER_BUF*PAGE_CACHE_SIZE)
155 
156 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
157 static unsigned buffer_blocknr[READ_BUFFERS];
158 static struct super_block *buffer_dev[READ_BUFFERS];
159 static int next_buffer;
160 
161 /*
162  * Returns a pointer to a buffer containing at least LEN bytes of
163  * filesystem starting at byte offset OFFSET into the filesystem.
164  */
165 static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
166 {
167         struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
168         struct page *pages[BLKS_PER_BUF];
169         unsigned i, blocknr, buffer;
170         unsigned long devsize;
171         char *data;
172 
173         if (!len)
174                 return NULL;
175         blocknr = offset >> PAGE_CACHE_SHIFT;
176         offset &= PAGE_CACHE_SIZE - 1;
177 
178         /* Check if an existing buffer already has the data.. */
179         for (i = 0; i < READ_BUFFERS; i++) {
180                 unsigned int blk_offset;
181 
182                 if (buffer_dev[i] != sb)
183                         continue;
184                 if (blocknr < buffer_blocknr[i])
185                         continue;
186                 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_CACHE_SHIFT;
187                 blk_offset += offset;
188                 if (blk_offset + len > BUFFER_SIZE)
189                         continue;
190                 return read_buffers[i] + blk_offset;
191         }
192 
193         devsize = mapping->host->i_size >> PAGE_CACHE_SHIFT;
194 
195         /* Ok, read in BLKS_PER_BUF pages completely first. */
196         for (i = 0; i < BLKS_PER_BUF; i++) {
197                 struct page *page = NULL;
198 
199                 if (blocknr + i < devsize) {
200                         page = read_mapping_page(mapping, blocknr + i, NULL);
201                         /* synchronous error? */
202                         if (IS_ERR(page))
203                                 page = NULL;
204                 }
205                 pages[i] = page;
206         }
207 
208         for (i = 0; i < BLKS_PER_BUF; i++) {
209                 struct page *page = pages[i];
210 
211                 if (page) {
212                         wait_on_page_locked(page);
213                         if (!PageUptodate(page)) {
214                                 /* asynchronous error */
215                                 page_cache_release(page);
216                                 pages[i] = NULL;
217                         }
218                 }
219         }
220 
221         buffer = next_buffer;
222         next_buffer = NEXT_BUFFER(buffer);
223         buffer_blocknr[buffer] = blocknr;
224         buffer_dev[buffer] = sb;
225 
226         data = read_buffers[buffer];
227         for (i = 0; i < BLKS_PER_BUF; i++) {
228                 struct page *page = pages[i];
229 
230                 if (page) {
231                         memcpy(data, kmap(page), PAGE_CACHE_SIZE);
232                         kunmap(page);
233                         page_cache_release(page);
234                 } else
235                         memset(data, 0, PAGE_CACHE_SIZE);
236                 data += PAGE_CACHE_SIZE;
237         }
238         return read_buffers[buffer] + offset;
239 }
240 
241 static void cramfs_kill_sb(struct super_block *sb)
242 {
243         struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
244 
245         kill_block_super(sb);
246         kfree(sbi);
247 }
248 
249 static int cramfs_remount(struct super_block *sb, int *flags, char *data)
250 {
251         sync_filesystem(sb);
252         *flags |= MS_RDONLY;
253         return 0;
254 }
255 
256 static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
257 {
258         int i;
259         struct cramfs_super super;
260         unsigned long root_offset;
261         struct cramfs_sb_info *sbi;
262         struct inode *root;
263 
264         sb->s_flags |= MS_RDONLY;
265 
266         sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
267         if (!sbi)
268                 return -ENOMEM;
269         sb->s_fs_info = sbi;
270 
271         /* Invalidate the read buffers on mount: think disk change.. */
272         mutex_lock(&read_mutex);
273         for (i = 0; i < READ_BUFFERS; i++)
274                 buffer_blocknr[i] = -1;
275 
276         /* Read the first block and get the superblock from it */
277         memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
278         mutex_unlock(&read_mutex);
279 
280         /* Do sanity checks on the superblock */
281         if (super.magic != CRAMFS_MAGIC) {
282                 /* check for wrong endianness */
283                 if (super.magic == CRAMFS_MAGIC_WEND) {
284                         if (!silent)
285                                 pr_err("wrong endianness\n");
286                         return -EINVAL;
287                 }
288 
289                 /* check at 512 byte offset */
290                 mutex_lock(&read_mutex);
291                 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
292                 mutex_unlock(&read_mutex);
293                 if (super.magic != CRAMFS_MAGIC) {
294                         if (super.magic == CRAMFS_MAGIC_WEND && !silent)
295                                 pr_err("wrong endianness\n");
296                         else if (!silent)
297                                 pr_err("wrong magic\n");
298                         return -EINVAL;
299                 }
300         }
301 
302         /* get feature flags first */
303         if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
304                 pr_err("unsupported filesystem features\n");
305                 return -EINVAL;
306         }
307 
308         /* Check that the root inode is in a sane state */
309         if (!S_ISDIR(super.root.mode)) {
310                 pr_err("root is not a directory\n");
311                 return -EINVAL;
312         }
313         /* correct strange, hard-coded permissions of mkcramfs */
314         super.root.mode |= (S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH);
315 
316         root_offset = super.root.offset << 2;
317         if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
318                 sbi->size = super.size;
319                 sbi->blocks = super.fsid.blocks;
320                 sbi->files = super.fsid.files;
321         } else {
322                 sbi->size = 1<<28;
323                 sbi->blocks = 0;
324                 sbi->files = 0;
325         }
326         sbi->magic = super.magic;
327         sbi->flags = super.flags;
328         if (root_offset == 0)
329                 pr_info("empty filesystem");
330         else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
331                  ((root_offset != sizeof(struct cramfs_super)) &&
332                   (root_offset != 512 + sizeof(struct cramfs_super))))
333         {
334                 pr_err("bad root offset %lu\n", root_offset);
335                 return -EINVAL;
336         }
337 
338         /* Set it all up.. */
339         sb->s_op = &cramfs_ops;
340         root = get_cramfs_inode(sb, &super.root, 0);
341         if (IS_ERR(root))
342                 return PTR_ERR(root);
343         sb->s_root = d_make_root(root);
344         if (!sb->s_root)
345                 return -ENOMEM;
346         return 0;
347 }
348 
349 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
350 {
351         struct super_block *sb = dentry->d_sb;
352         u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
353 
354         buf->f_type = CRAMFS_MAGIC;
355         buf->f_bsize = PAGE_CACHE_SIZE;
356         buf->f_blocks = CRAMFS_SB(sb)->blocks;
357         buf->f_bfree = 0;
358         buf->f_bavail = 0;
359         buf->f_files = CRAMFS_SB(sb)->files;
360         buf->f_ffree = 0;
361         buf->f_fsid.val[0] = (u32)id;
362         buf->f_fsid.val[1] = (u32)(id >> 32);
363         buf->f_namelen = CRAMFS_MAXPATHLEN;
364         return 0;
365 }
366 
367 /*
368  * Read a cramfs directory entry.
369  */
370 static int cramfs_readdir(struct file *file, struct dir_context *ctx)
371 {
372         struct inode *inode = file_inode(file);
373         struct super_block *sb = inode->i_sb;
374         char *buf;
375         unsigned int offset;
376 
377         /* Offset within the thing. */
378         if (ctx->pos >= inode->i_size)
379                 return 0;
380         offset = ctx->pos;
381         /* Directory entries are always 4-byte aligned */
382         if (offset & 3)
383                 return -EINVAL;
384 
385         buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
386         if (!buf)
387                 return -ENOMEM;
388 
389         while (offset < inode->i_size) {
390                 struct cramfs_inode *de;
391                 unsigned long nextoffset;
392                 char *name;
393                 ino_t ino;
394                 umode_t mode;
395                 int namelen;
396 
397                 mutex_lock(&read_mutex);
398                 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
399                 name = (char *)(de+1);
400 
401                 /*
402                  * Namelengths on disk are shifted by two
403                  * and the name padded out to 4-byte boundaries
404                  * with zeroes.
405                  */
406                 namelen = de->namelen << 2;
407                 memcpy(buf, name, namelen);
408                 ino = cramino(de, OFFSET(inode) + offset);
409                 mode = de->mode;
410                 mutex_unlock(&read_mutex);
411                 nextoffset = offset + sizeof(*de) + namelen;
412                 for (;;) {
413                         if (!namelen) {
414                                 kfree(buf);
415                                 return -EIO;
416                         }
417                         if (buf[namelen-1])
418                                 break;
419                         namelen--;
420                 }
421                 if (!dir_emit(ctx, buf, namelen, ino, mode >> 12))
422                         break;
423 
424                 ctx->pos = offset = nextoffset;
425         }
426         kfree(buf);
427         return 0;
428 }
429 
430 /*
431  * Lookup and fill in the inode data..
432  */
433 static struct dentry *cramfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
434 {
435         unsigned int offset = 0;
436         struct inode *inode = NULL;
437         int sorted;
438 
439         mutex_lock(&read_mutex);
440         sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
441         while (offset < dir->i_size) {
442                 struct cramfs_inode *de;
443                 char *name;
444                 int namelen, retval;
445                 int dir_off = OFFSET(dir) + offset;
446 
447                 de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN);
448                 name = (char *)(de+1);
449 
450                 /* Try to take advantage of sorted directories */
451                 if (sorted && (dentry->d_name.name[0] < name[0]))
452                         break;
453 
454                 namelen = de->namelen << 2;
455                 offset += sizeof(*de) + namelen;
456 
457                 /* Quick check that the name is roughly the right length */
458                 if (((dentry->d_name.len + 3) & ~3) != namelen)
459                         continue;
460 
461                 for (;;) {
462                         if (!namelen) {
463                                 inode = ERR_PTR(-EIO);
464                                 goto out;
465                         }
466                         if (name[namelen-1])
467                                 break;
468                         namelen--;
469                 }
470                 if (namelen != dentry->d_name.len)
471                         continue;
472                 retval = memcmp(dentry->d_name.name, name, namelen);
473                 if (retval > 0)
474                         continue;
475                 if (!retval) {
476                         inode = get_cramfs_inode(dir->i_sb, de, dir_off);
477                         break;
478                 }
479                 /* else (retval < 0) */
480                 if (sorted)
481                         break;
482         }
483 out:
484         mutex_unlock(&read_mutex);
485         if (IS_ERR(inode))
486                 return ERR_CAST(inode);
487         d_add(dentry, inode);
488         return NULL;
489 }
490 
491 static int cramfs_readpage(struct file *file, struct page *page)
492 {
493         struct inode *inode = page->mapping->host;
494         u32 maxblock;
495         int bytes_filled;
496         void *pgdata;
497 
498         maxblock = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
499         bytes_filled = 0;
500         pgdata = kmap(page);
501 
502         if (page->index < maxblock) {
503                 struct super_block *sb = inode->i_sb;
504                 u32 blkptr_offset = OFFSET(inode) + page->index*4;
505                 u32 start_offset, compr_len;
506 
507                 start_offset = OFFSET(inode) + maxblock*4;
508                 mutex_lock(&read_mutex);
509                 if (page->index)
510                         start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4,
511                                 4);
512                 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) -
513                         start_offset);
514                 mutex_unlock(&read_mutex);
515 
516                 if (compr_len == 0)
517                         ; /* hole */
518                 else if (unlikely(compr_len > (PAGE_CACHE_SIZE << 1))) {
519                         pr_err("bad compressed blocksize %u\n",
520                                 compr_len);
521                         goto err;
522                 } else {
523                         mutex_lock(&read_mutex);
524                         bytes_filled = cramfs_uncompress_block(pgdata,
525                                  PAGE_CACHE_SIZE,
526                                  cramfs_read(sb, start_offset, compr_len),
527                                  compr_len);
528                         mutex_unlock(&read_mutex);
529                         if (unlikely(bytes_filled < 0))
530                                 goto err;
531                 }
532         }
533 
534         memset(pgdata + bytes_filled, 0, PAGE_CACHE_SIZE - bytes_filled);
535         flush_dcache_page(page);
536         kunmap(page);
537         SetPageUptodate(page);
538         unlock_page(page);
539         return 0;
540 
541 err:
542         kunmap(page);
543         ClearPageUptodate(page);
544         SetPageError(page);
545         unlock_page(page);
546         return 0;
547 }
548 
549 static const struct address_space_operations cramfs_aops = {
550         .readpage = cramfs_readpage
551 };
552 
553 /*
554  * Our operations:
555  */
556 
557 /*
558  * A directory can only readdir
559  */
560 static const struct file_operations cramfs_directory_operations = {
561         .llseek         = generic_file_llseek,
562         .read           = generic_read_dir,
563         .iterate        = cramfs_readdir,
564 };
565 
566 static const struct inode_operations cramfs_dir_inode_operations = {
567         .lookup         = cramfs_lookup,
568 };
569 
570 static const struct super_operations cramfs_ops = {
571         .remount_fs     = cramfs_remount,
572         .statfs         = cramfs_statfs,
573 };
574 
575 static struct dentry *cramfs_mount(struct file_system_type *fs_type,
576         int flags, const char *dev_name, void *data)
577 {
578         return mount_bdev(fs_type, flags, dev_name, data, cramfs_fill_super);
579 }
580 
581 static struct file_system_type cramfs_fs_type = {
582         .owner          = THIS_MODULE,
583         .name           = "cramfs",
584         .mount          = cramfs_mount,
585         .kill_sb        = cramfs_kill_sb,
586         .fs_flags       = FS_REQUIRES_DEV,
587 };
588 MODULE_ALIAS_FS("cramfs");
589 
590 static int __init init_cramfs_fs(void)
591 {
592         int rv;
593 
594         rv = cramfs_uncompress_init();
595         if (rv < 0)
596                 return rv;
597         rv = register_filesystem(&cramfs_fs_type);
598         if (rv < 0)
599                 cramfs_uncompress_exit();
600         return rv;
601 }
602 
603 static void __exit exit_cramfs_fs(void)
604 {
605         cramfs_uncompress_exit();
606         unregister_filesystem(&cramfs_fs_type);
607 }
608 
609 module_init(init_cramfs_fs)
610 module_exit(exit_cramfs_fs)
611 MODULE_LICENSE("GPL");
612 

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