fs/cramfs/inode.c

   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");