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_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_CACHE_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_CACHE_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_CACHE_SHIFT;
 177         offset &= PAGE_CACHE_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_CACHE_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_CACHE_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                                 page_cache_release(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_CACHE_SIZE);
 233                         kunmap(page);
 234                         page_cache_release(page);
 235                 } else
 236                         memset(data, 0, PAGE_CACHE_SIZE);
 237                 data += PAGE_CACHE_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_CACHE_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_CACHE_SIZE - 1) >> PAGE_CACHE_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_CACHE_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_CACHE_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_CACHE_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");