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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_nohighmem(inode);
104                 inode->i_data.a_ops = &cramfs_aops;
105                 break;
106         default:
107                 init_special_inode(inode, cramfs_inode->mode,
108                                 old_decode_dev(cramfs_inode->size));
109         }
110 
111         inode->i_mode = cramfs_inode->mode;
112         i_uid_write(inode, cramfs_inode->uid);
113         i_gid_write(inode, cramfs_inode->gid);
114 
115         /* if the lower 2 bits are zero, the inode contains data */
116         if (!(inode->i_ino & 3)) {
117                 inode->i_size = cramfs_inode->size;
118                 inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
119         }
120 
121         /* Struct copy intentional */
122         inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
123         /* inode->i_nlink is left 1 - arguably wrong for directories,
124            but it's the best we can do without reading the directory
125            contents.  1 yields the right result in GNU find, even
126            without -noleaf option. */
127 
128         unlock_new_inode(inode);
129 
130         return inode;
131 }
132 
133 /*
134  * We have our own block cache: don't fill up the buffer cache
135  * with the rom-image, because the way the filesystem is set
136  * up the accesses should be fairly regular and cached in the
137  * page cache and dentry tree anyway..
138  *
139  * This also acts as a way to guarantee contiguous areas of up to
140  * BLKS_PER_BUF*PAGE_SIZE, so that the caller doesn't need to
141  * worry about end-of-buffer issues even when decompressing a full
142  * page cache.
143  */
144 #define READ_BUFFERS (2)
145 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
146 #define NEXT_BUFFER(_ix) ((_ix) ^ 1)
147 
148 /*
149  * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
150  * data that takes up more space than the original and with unlucky
151  * alignment.
152  */
153 #define BLKS_PER_BUF_SHIFT      (2)
154 #define BLKS_PER_BUF            (1 << BLKS_PER_BUF_SHIFT)
155 #define BUFFER_SIZE             (BLKS_PER_BUF*PAGE_SIZE)
156 
157 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
158 static unsigned buffer_blocknr[READ_BUFFERS];
159 static struct super_block *buffer_dev[READ_BUFFERS];
160 static int next_buffer;
161 
162 /*
163  * Returns a pointer to a buffer containing at least LEN bytes of
164  * filesystem starting at byte offset OFFSET into the filesystem.
165  */
166 static void *cramfs_read(struct super_block *sb, unsigned int offset, unsigned int len)
167 {
168         struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
169         struct page *pages[BLKS_PER_BUF];
170         unsigned i, blocknr, buffer;
171         unsigned long devsize;
172         char *data;
173 
174         if (!len)
175                 return NULL;
176         blocknr = offset >> PAGE_SHIFT;
177         offset &= PAGE_SIZE - 1;
178 
179         /* Check if an existing buffer already has the data.. */
180         for (i = 0; i < READ_BUFFERS; i++) {
181                 unsigned int blk_offset;
182 
183                 if (buffer_dev[i] != sb)
184                         continue;
185                 if (blocknr < buffer_blocknr[i])
186                         continue;
187                 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_SHIFT;
188                 blk_offset += offset;
189                 if (blk_offset + len > BUFFER_SIZE)
190                         continue;
191                 return read_buffers[i] + blk_offset;
192         }
193 
194         devsize = mapping->host->i_size >> PAGE_SHIFT;
195 
196         /* Ok, read in BLKS_PER_BUF pages completely first. */
197         for (i = 0; i < BLKS_PER_BUF; i++) {
198                 struct page *page = NULL;
199 
200                 if (blocknr + i < devsize) {
201                         page = read_mapping_page(mapping, blocknr + i, NULL);
202                         /* synchronous error? */
203                         if (IS_ERR(page))
204                                 page = NULL;
205                 }
206                 pages[i] = page;
207         }
208 
209         for (i = 0; i < BLKS_PER_BUF; i++) {
210                 struct page *page = pages[i];
211 
212                 if (page) {
213                         wait_on_page_locked(page);
214                         if (!PageUptodate(page)) {
215                                 /* asynchronous error */
216                                 put_page(page);
217                                 pages[i] = NULL;
218                         }
219                 }
220         }
221 
222         buffer = next_buffer;
223         next_buffer = NEXT_BUFFER(buffer);
224         buffer_blocknr[buffer] = blocknr;
225         buffer_dev[buffer] = sb;
226 
227         data = read_buffers[buffer];
228         for (i = 0; i < BLKS_PER_BUF; i++) {
229                 struct page *page = pages[i];
230 
231                 if (page) {
232                         memcpy(data, kmap(page), PAGE_SIZE);
233                         kunmap(page);
234                         put_page(page);
235                 } else
236                         memset(data, 0, PAGE_SIZE);
237                 data += PAGE_SIZE;
238         }
239         return read_buffers[buffer] + offset;
240 }
241 
242 static void cramfs_kill_sb(struct super_block *sb)
243 {
244         struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
245 
246         kill_block_super(sb);
247         kfree(sbi);
248 }
249 
250 static int cramfs_remount(struct super_block *sb, int *flags, char *data)
251 {
252         sync_filesystem(sb);
253         *flags |= MS_RDONLY;
254         return 0;
255 }
256 
257 static int cramfs_fill_super(struct super_block *sb, void *data, int silent)
258 {
259         int i;
260         struct cramfs_super super;
261         unsigned long root_offset;
262         struct cramfs_sb_info *sbi;
263         struct inode *root;
264 
265         sb->s_flags |= MS_RDONLY;
266 
267         sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
268         if (!sbi)
269                 return -ENOMEM;
270         sb->s_fs_info = sbi;
271 
272         /* Invalidate the read buffers on mount: think disk change.. */
273         mutex_lock(&read_mutex);
274         for (i = 0; i < READ_BUFFERS; i++)
275                 buffer_blocknr[i] = -1;
276 
277         /* Read the first block and get the superblock from it */
278         memcpy(&super, cramfs_read(sb, 0, sizeof(super)), sizeof(super));
279         mutex_unlock(&read_mutex);
280 
281         /* Do sanity checks on the superblock */
282         if (super.magic != CRAMFS_MAGIC) {
283                 /* check for wrong endianness */
284                 if (super.magic == CRAMFS_MAGIC_WEND) {
285                         if (!silent)
286                                 pr_err("wrong endianness\n");
287                         return -EINVAL;
288                 }
289 
290                 /* check at 512 byte offset */
291                 mutex_lock(&read_mutex);
292                 memcpy(&super, cramfs_read(sb, 512, sizeof(super)), sizeof(super));
293                 mutex_unlock(&read_mutex);
294                 if (super.magic != CRAMFS_MAGIC) {
295                         if (super.magic == CRAMFS_MAGIC_WEND && !silent)
296                                 pr_err("wrong endianness\n");
297                         else if (!silent)
298                                 pr_err("wrong magic\n");
299                         return -EINVAL;
300                 }
301         }
302 
303         /* get feature flags first */
304         if (super.flags & ~CRAMFS_SUPPORTED_FLAGS) {
305                 pr_err("unsupported filesystem features\n");
306                 return -EINVAL;
307         }
308 
309         /* Check that the root inode is in a sane state */
310         if (!S_ISDIR(super.root.mode)) {
311                 pr_err("root is not a directory\n");
312                 return -EINVAL;
313         }
314         /* correct strange, hard-coded permissions of mkcramfs */
315         super.root.mode |= (S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH);
316 
317         root_offset = super.root.offset << 2;
318         if (super.flags & CRAMFS_FLAG_FSID_VERSION_2) {
319                 sbi->size = super.size;
320                 sbi->blocks = super.fsid.blocks;
321                 sbi->files = super.fsid.files;
322         } else {
323                 sbi->size = 1<<28;
324                 sbi->blocks = 0;
325                 sbi->files = 0;
326         }
327         sbi->magic = super.magic;
328         sbi->flags = super.flags;
329         if (root_offset == 0)
330                 pr_info("empty filesystem");
331         else if (!(super.flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
332                  ((root_offset != sizeof(struct cramfs_super)) &&
333                   (root_offset != 512 + sizeof(struct cramfs_super))))
334         {
335                 pr_err("bad root offset %lu\n", root_offset);
336                 return -EINVAL;
337         }
338 
339         /* Set it all up.. */
340         sb->s_op = &cramfs_ops;
341         root = get_cramfs_inode(sb, &super.root, 0);
342         if (IS_ERR(root))
343                 return PTR_ERR(root);
344         sb->s_root = d_make_root(root);
345         if (!sb->s_root)
346                 return -ENOMEM;
347         return 0;
348 }
349 
350 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
351 {
352         struct super_block *sb = dentry->d_sb;
353         u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
354 
355         buf->f_type = CRAMFS_MAGIC;
356         buf->f_bsize = PAGE_SIZE;
357         buf->f_blocks = CRAMFS_SB(sb)->blocks;
358         buf->f_bfree = 0;
359         buf->f_bavail = 0;
360         buf->f_files = CRAMFS_SB(sb)->files;
361         buf->f_ffree = 0;
362         buf->f_fsid.val[0] = (u32)id;
363         buf->f_fsid.val[1] = (u32)(id >> 32);
364         buf->f_namelen = CRAMFS_MAXPATHLEN;
365         return 0;
366 }
367 
368 /*
369  * Read a cramfs directory entry.
370  */
371 static int cramfs_readdir(struct file *file, struct dir_context *ctx)
372 {
373         struct inode *inode = file_inode(file);
374         struct super_block *sb = inode->i_sb;
375         char *buf;
376         unsigned int offset;
377 
378         /* Offset within the thing. */
379         if (ctx->pos >= inode->i_size)
380                 return 0;
381         offset = ctx->pos;
382         /* Directory entries are always 4-byte aligned */
383         if (offset & 3)
384                 return -EINVAL;
385 
386         buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
387         if (!buf)
388                 return -ENOMEM;
389 
390         while (offset < inode->i_size) {
391                 struct cramfs_inode *de;
392                 unsigned long nextoffset;
393                 char *name;
394                 ino_t ino;
395                 umode_t mode;
396                 int namelen;
397 
398                 mutex_lock(&read_mutex);
399                 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
400                 name = (char *)(de+1);
401 
402                 /*
403                  * Namelengths on disk are shifted by two
404                  * and the name padded out to 4-byte boundaries
405                  * with zeroes.
406                  */
407                 namelen = de->namelen << 2;
408                 memcpy(buf, name, namelen);
409                 ino = cramino(de, OFFSET(inode) + offset);
410                 mode = de->mode;
411                 mutex_unlock(&read_mutex);
412                 nextoffset = offset + sizeof(*de) + namelen;
413                 for (;;) {
414                         if (!namelen) {
415                                 kfree(buf);
416                                 return -EIO;
417                         }
418                         if (buf[namelen-1])
419                                 break;
420                         namelen--;
421                 }
422                 if (!dir_emit(ctx, buf, namelen, ino, mode >> 12))
423                         break;
424 
425                 ctx->pos = offset = nextoffset;
426         }
427         kfree(buf);
428         return 0;
429 }
430 
431 /*
432  * Lookup and fill in the inode data..
433  */
434 static struct dentry *cramfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
435 {
436         unsigned int offset = 0;
437         struct inode *inode = NULL;
438         int sorted;
439 
440         mutex_lock(&read_mutex);
441         sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
442         while (offset < dir->i_size) {
443                 struct cramfs_inode *de;
444                 char *name;
445                 int namelen, retval;
446                 int dir_off = OFFSET(dir) + offset;
447 
448                 de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN);
449                 name = (char *)(de+1);
450 
451                 /* Try to take advantage of sorted directories */
452                 if (sorted && (dentry->d_name.name[0] < name[0]))
453                         break;
454 
455                 namelen = de->namelen << 2;
456                 offset += sizeof(*de) + namelen;
457 
458                 /* Quick check that the name is roughly the right length */
459                 if (((dentry->d_name.len + 3) & ~3) != namelen)
460                         continue;
461 
462                 for (;;) {
463                         if (!namelen) {
464                                 inode = ERR_PTR(-EIO);
465                                 goto out;
466                         }
467                         if (name[namelen-1])
468                                 break;
469                         namelen--;
470                 }
471                 if (namelen != dentry->d_name.len)
472                         continue;
473                 retval = memcmp(dentry->d_name.name, name, namelen);
474                 if (retval > 0)
475                         continue;
476                 if (!retval) {
477                         inode = get_cramfs_inode(dir->i_sb, de, dir_off);
478                         break;
479                 }
480                 /* else (retval < 0) */
481                 if (sorted)
482                         break;
483         }
484 out:
485         mutex_unlock(&read_mutex);
486         if (IS_ERR(inode))
487                 return ERR_CAST(inode);
488         d_add(dentry, inode);
489         return NULL;
490 }
491 
492 static int cramfs_readpage(struct file *file, struct page *page)
493 {
494         struct inode *inode = page->mapping->host;
495         u32 maxblock;
496         int bytes_filled;
497         void *pgdata;
498 
499         maxblock = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
500         bytes_filled = 0;
501         pgdata = kmap(page);
502 
503         if (page->index < maxblock) {
504                 struct super_block *sb = inode->i_sb;
505                 u32 blkptr_offset = OFFSET(inode) + page->index*4;
506                 u32 start_offset, compr_len;
507 
508                 start_offset = OFFSET(inode) + maxblock*4;
509                 mutex_lock(&read_mutex);
510                 if (page->index)
511                         start_offset = *(u32 *) cramfs_read(sb, blkptr_offset-4,
512                                 4);
513                 compr_len = (*(u32 *) cramfs_read(sb, blkptr_offset, 4) -
514                         start_offset);
515                 mutex_unlock(&read_mutex);
516 
517                 if (compr_len == 0)
518                         ; /* hole */
519                 else if (unlikely(compr_len > (PAGE_SIZE << 1))) {
520                         pr_err("bad compressed blocksize %u\n",
521                                 compr_len);
522                         goto err;
523                 } else {
524                         mutex_lock(&read_mutex);
525                         bytes_filled = cramfs_uncompress_block(pgdata,
526                                  PAGE_SIZE,
527                                  cramfs_read(sb, start_offset, compr_len),
528                                  compr_len);
529                         mutex_unlock(&read_mutex);
530                         if (unlikely(bytes_filled < 0))
531                                 goto err;
532                 }
533         }
534 
535         memset(pgdata + bytes_filled, 0, PAGE_SIZE - bytes_filled);
536         flush_dcache_page(page);
537         kunmap(page);
538         SetPageUptodate(page);
539         unlock_page(page);
540         return 0;
541 
542 err:
543         kunmap(page);
544         ClearPageUptodate(page);
545         SetPageError(page);
546         unlock_page(page);
547         return 0;
548 }
549 
550 static const struct address_space_operations cramfs_aops = {
551         .readpage = cramfs_readpage
552 };
553 
554 /*
555  * Our operations:
556  */
557 
558 /*
559  * A directory can only readdir
560  */
561 static const struct file_operations cramfs_directory_operations = {
562         .llseek         = generic_file_llseek,
563         .read           = generic_read_dir,
564         .iterate        = cramfs_readdir,
565 };
566 
567 static const struct inode_operations cramfs_dir_inode_operations = {
568         .lookup         = cramfs_lookup,
569 };
570 
571 static const struct super_operations cramfs_ops = {
572         .remount_fs     = cramfs_remount,
573         .statfs         = cramfs_statfs,
574 };
575 
576 static struct dentry *cramfs_mount(struct file_system_type *fs_type,
577         int flags, const char *dev_name, void *data)
578 {
579         return mount_bdev(fs_type, flags, dev_name, data, cramfs_fill_super);
580 }
581 
582 static struct file_system_type cramfs_fs_type = {
583         .owner          = THIS_MODULE,
584         .name           = "cramfs",
585         .mount          = cramfs_mount,
586         .kill_sb        = cramfs_kill_sb,
587         .fs_flags       = FS_REQUIRES_DEV,
588 };
589 MODULE_ALIAS_FS("cramfs");
590 
591 static int __init init_cramfs_fs(void)
592 {
593         int rv;
594 
595         rv = cramfs_uncompress_init();
596         if (rv < 0)
597                 return rv;
598         rv = register_filesystem(&cramfs_fs_type);
599         if (rv < 0)
600                 cramfs_uncompress_exit();
601         return rv;
602 }
603 
604 static void __exit exit_cramfs_fs(void)
605 {
606         cramfs_uncompress_exit();
607         unregister_filesystem(&cramfs_fs_type);
608 }
609 
610 module_init(init_cramfs_fs)
611 module_exit(exit_cramfs_fs)
612 MODULE_LICENSE("GPL");
613 

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