fs/cramfs/inode.c

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This source file includes following definitions.
CRAMFS_SB
cramino
get_cramfs_inode
cramfs_blkdev_read
cramfs_direct_read
cramfs_read
cramfs_get_block_range
cramfs_last_page_is_shared
cramfs_physmem_mmap
cramfs_physmem_mmap
cramfs_physmem_get_unmapped_area
cramfs_physmem_mmap_capabilities
cramfs_kill_sb
cramfs_reconfigure
cramfs_read_super
cramfs_finalize_super
cramfs_blkdev_fill_super
cramfs_mtd_fill_super
cramfs_statfs
cramfs_readdir
cramfs_lookup
cramfs_readpage
cramfs_get_tree
cramfs_init_fs_context
init_cramfs_fs
exit_cramfs_fs
   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/file.h>
  19 #include <linux/pagemap.h>
  20 #include <linux/pfn_t.h>
  21 #include <linux/ramfs.h>
  22 #include <linux/init.h>
  23 #include <linux/string.h>
  24 #include <linux/blkdev.h>
  25 #include <linux/mtd/mtd.h>
  26 #include <linux/mtd/super.h>
  27 #include <linux/fs_context.h>
  28 #include <linux/slab.h>
  29 #include <linux/vfs.h>
  30 #include <linux/mutex.h>
  31 #include <uapi/linux/cramfs_fs.h>
  32 #include <linux/uaccess.h>
  33 
  34 #include "internal.h"
  35 
  36 /*
  37  * cramfs super-block data in memory
  38  */
  39 struct cramfs_sb_info {
  40         unsigned long magic;
  41         unsigned long size;
  42         unsigned long blocks;
  43         unsigned long files;
  44         unsigned long flags;
  45         void *linear_virt_addr;
  46         resource_size_t linear_phys_addr;
  47         size_t mtd_point_size;
  48 };
  49 
  50 static inline struct cramfs_sb_info *CRAMFS_SB(struct super_block *sb)
  51 {
  52         return sb->s_fs_info;
  53 }
  54 
  55 static const struct super_operations cramfs_ops;
  56 static const struct inode_operations cramfs_dir_inode_operations;
  57 static const struct file_operations cramfs_directory_operations;
  58 static const struct file_operations cramfs_physmem_fops;
  59 static const struct address_space_operations cramfs_aops;
  60 
  61 static DEFINE_MUTEX(read_mutex);
  62 
  63 
  64 /* These macros may change in future, to provide better st_ino semantics. */
  65 #define OFFSET(x)       ((x)->i_ino)
  66 
  67 static unsigned long cramino(const struct cramfs_inode *cino, unsigned int offset)
  68 {
  69         if (!cino->offset)
  70                 return offset + 1;
  71         if (!cino->size)
  72                 return offset + 1;
  73 
  74         /*
  75          * The file mode test fixes buggy mkcramfs implementations where
  76          * cramfs_inode->offset is set to a non zero value for entries
  77          * which did not contain data, like devices node and fifos.
  78          */
  79         switch (cino->mode & S_IFMT) {
  80         case S_IFREG:
  81         case S_IFDIR:
  82         case S_IFLNK:
  83                 return cino->offset << 2;
  84         default:
  85                 break;
  86         }
  87         return offset + 1;
  88 }
  89 
  90 static struct inode *get_cramfs_inode(struct super_block *sb,
  91         const struct cramfs_inode *cramfs_inode, unsigned int offset)
  92 {
  93         struct inode *inode;
  94         static struct timespec64 zerotime;
  95 
  96         inode = iget_locked(sb, cramino(cramfs_inode, offset));
  97         if (!inode)
  98                 return ERR_PTR(-ENOMEM);
  99         if (!(inode->i_state & I_NEW))
 100                 return inode;
 101 
 102         switch (cramfs_inode->mode & S_IFMT) {
 103         case S_IFREG:
 104                 inode->i_fop = &generic_ro_fops;
 105                 inode->i_data.a_ops = &cramfs_aops;
 106                 if (IS_ENABLED(CONFIG_CRAMFS_MTD) &&
 107                     CRAMFS_SB(sb)->flags & CRAMFS_FLAG_EXT_BLOCK_POINTERS &&
 108                     CRAMFS_SB(sb)->linear_phys_addr)
 109                         inode->i_fop = &cramfs_physmem_fops;
 110                 break;
 111         case S_IFDIR:
 112                 inode->i_op = &cramfs_dir_inode_operations;
 113                 inode->i_fop = &cramfs_directory_operations;
 114                 break;
 115         case S_IFLNK:
 116                 inode->i_op = &page_symlink_inode_operations;
 117                 inode_nohighmem(inode);
 118                 inode->i_data.a_ops = &cramfs_aops;
 119                 break;
 120         default:
 121                 init_special_inode(inode, cramfs_inode->mode,
 122                                 old_decode_dev(cramfs_inode->size));
 123         }
 124 
 125         inode->i_mode = cramfs_inode->mode;
 126         i_uid_write(inode, cramfs_inode->uid);
 127         i_gid_write(inode, cramfs_inode->gid);
 128 
 129         /* if the lower 2 bits are zero, the inode contains data */
 130         if (!(inode->i_ino & 3)) {
 131                 inode->i_size = cramfs_inode->size;
 132                 inode->i_blocks = (cramfs_inode->size - 1) / 512 + 1;
 133         }
 134 
 135         /* Struct copy intentional */
 136         inode->i_mtime = inode->i_atime = inode->i_ctime = zerotime;
 137         /* inode->i_nlink is left 1 - arguably wrong for directories,
 138            but it's the best we can do without reading the directory
 139            contents.  1 yields the right result in GNU find, even
 140            without -noleaf option. */
 141 
 142         unlock_new_inode(inode);
 143 
 144         return inode;
 145 }
 146 
 147 /*
 148  * We have our own block cache: don't fill up the buffer cache
 149  * with the rom-image, because the way the filesystem is set
 150  * up the accesses should be fairly regular and cached in the
 151  * page cache and dentry tree anyway..
 152  *
 153  * This also acts as a way to guarantee contiguous areas of up to
 154  * BLKS_PER_BUF*PAGE_SIZE, so that the caller doesn't need to
 155  * worry about end-of-buffer issues even when decompressing a full
 156  * page cache.
 157  *
 158  * Note: This is all optimized away at compile time when
 159  *       CONFIG_CRAMFS_BLOCKDEV=n.
 160  */
 161 #define READ_BUFFERS (2)
 162 /* NEXT_BUFFER(): Loop over [0..(READ_BUFFERS-1)]. */
 163 #define NEXT_BUFFER(_ix) ((_ix) ^ 1)
 164 
 165 /*
 166  * BLKS_PER_BUF_SHIFT should be at least 2 to allow for "compressed"
 167  * data that takes up more space than the original and with unlucky
 168  * alignment.
 169  */
 170 #define BLKS_PER_BUF_SHIFT      (2)
 171 #define BLKS_PER_BUF            (1 << BLKS_PER_BUF_SHIFT)
 172 #define BUFFER_SIZE             (BLKS_PER_BUF*PAGE_SIZE)
 173 
 174 static unsigned char read_buffers[READ_BUFFERS][BUFFER_SIZE];
 175 static unsigned buffer_blocknr[READ_BUFFERS];
 176 static struct super_block *buffer_dev[READ_BUFFERS];
 177 static int next_buffer;
 178 
 179 /*
 180  * Populate our block cache and return a pointer to it.
 181  */
 182 static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
 183                                 unsigned int len)
 184 {
 185         struct address_space *mapping = sb->s_bdev->bd_inode->i_mapping;
 186         struct page *pages[BLKS_PER_BUF];
 187         unsigned i, blocknr, buffer;
 188         unsigned long devsize;
 189         char *data;
 190 
 191         if (!len)
 192                 return NULL;
 193         blocknr = offset >> PAGE_SHIFT;
 194         offset &= PAGE_SIZE - 1;
 195 
 196         /* Check if an existing buffer already has the data.. */
 197         for (i = 0; i < READ_BUFFERS; i++) {
 198                 unsigned int blk_offset;
 199 
 200                 if (buffer_dev[i] != sb)
 201                         continue;
 202                 if (blocknr < buffer_blocknr[i])
 203                         continue;
 204                 blk_offset = (blocknr - buffer_blocknr[i]) << PAGE_SHIFT;
 205                 blk_offset += offset;
 206                 if (blk_offset > BUFFER_SIZE ||
 207                     blk_offset + len > BUFFER_SIZE)
 208                         continue;
 209                 return read_buffers[i] + blk_offset;
 210         }
 211 
 212         devsize = mapping->host->i_size >> PAGE_SHIFT;
 213 
 214         /* Ok, read in BLKS_PER_BUF pages completely first. */
 215         for (i = 0; i < BLKS_PER_BUF; i++) {
 216                 struct page *page = NULL;
 217 
 218                 if (blocknr + i < devsize) {
 219                         page = read_mapping_page(mapping, blocknr + i, NULL);
 220                         /* synchronous error? */
 221                         if (IS_ERR(page))
 222                                 page = NULL;
 223                 }
 224                 pages[i] = page;
 225         }
 226 
 227         for (i = 0; i < BLKS_PER_BUF; i++) {
 228                 struct page *page = pages[i];
 229 
 230                 if (page) {
 231                         wait_on_page_locked(page);
 232                         if (!PageUptodate(page)) {
 233                                 /* asynchronous error */
 234                                 put_page(page);
 235                                 pages[i] = NULL;
 236                         }
 237                 }
 238         }
 239 
 240         buffer = next_buffer;
 241         next_buffer = NEXT_BUFFER(buffer);
 242         buffer_blocknr[buffer] = blocknr;
 243         buffer_dev[buffer] = sb;
 244 
 245         data = read_buffers[buffer];
 246         for (i = 0; i < BLKS_PER_BUF; i++) {
 247                 struct page *page = pages[i];
 248 
 249                 if (page) {
 250                         memcpy(data, kmap(page), PAGE_SIZE);
 251                         kunmap(page);
 252                         put_page(page);
 253                 } else
 254                         memset(data, 0, PAGE_SIZE);
 255                 data += PAGE_SIZE;
 256         }
 257         return read_buffers[buffer] + offset;
 258 }
 259 
 260 /*
 261  * Return a pointer to the linearly addressed cramfs image in memory.
 262  */
 263 static void *cramfs_direct_read(struct super_block *sb, unsigned int offset,
 264                                 unsigned int len)
 265 {
 266         struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
 267 
 268         if (!len)
 269                 return NULL;
 270         if (len > sbi->size || offset > sbi->size - len)
 271                 return page_address(ZERO_PAGE(0));
 272         return sbi->linear_virt_addr + offset;
 273 }
 274 
 275 /*
 276  * Returns a pointer to a buffer containing at least LEN bytes of
 277  * filesystem starting at byte offset OFFSET into the filesystem.
 278  */
 279 static void *cramfs_read(struct super_block *sb, unsigned int offset,
 280                          unsigned int len)
 281 {
 282         struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
 283 
 284         if (IS_ENABLED(CONFIG_CRAMFS_MTD) && sbi->linear_virt_addr)
 285                 return cramfs_direct_read(sb, offset, len);
 286         else if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV))
 287                 return cramfs_blkdev_read(sb, offset, len);
 288         else
 289                 return NULL;
 290 }
 291 
 292 /*
 293  * For a mapping to be possible, we need a range of uncompressed and
 294  * contiguous blocks. Return the offset for the first block and number of
 295  * valid blocks for which that is true, or zero otherwise.
 296  */
 297 static u32 cramfs_get_block_range(struct inode *inode, u32 pgoff, u32 *pages)
 298 {
 299         struct cramfs_sb_info *sbi = CRAMFS_SB(inode->i_sb);
 300         int i;
 301         u32 *blockptrs, first_block_addr;
 302 
 303         /*
 304          * We can dereference memory directly here as this code may be
 305          * reached only when there is a direct filesystem image mapping
 306          * available in memory.
 307          */
 308         blockptrs = (u32 *)(sbi->linear_virt_addr + OFFSET(inode) + pgoff * 4);
 309         first_block_addr = blockptrs[0] & ~CRAMFS_BLK_FLAGS;
 310         i = 0;
 311         do {
 312                 u32 block_off = i * (PAGE_SIZE >> CRAMFS_BLK_DIRECT_PTR_SHIFT);
 313                 u32 expect = (first_block_addr + block_off) |
 314                              CRAMFS_BLK_FLAG_DIRECT_PTR |
 315                              CRAMFS_BLK_FLAG_UNCOMPRESSED;
 316                 if (blockptrs[i] != expect) {
 317                         pr_debug("range: block %d/%d got %#x expects %#x\n",
 318                                  pgoff+i, pgoff + *pages - 1,
 319                                  blockptrs[i], expect);
 320                         if (i == 0)
 321                                 return 0;
 322                         break;
 323                 }
 324         } while (++i < *pages);
 325 
 326         *pages = i;
 327         return first_block_addr << CRAMFS_BLK_DIRECT_PTR_SHIFT;
 328 }
 329 
 330 #ifdef CONFIG_MMU
 331 
 332 /*
 333  * Return true if the last page of a file in the filesystem image contains
 334  * some other data that doesn't belong to that file. It is assumed that the
 335  * last block is CRAMFS_BLK_FLAG_DIRECT_PTR | CRAMFS_BLK_FLAG_UNCOMPRESSED
 336  * (verified by cramfs_get_block_range() and directly accessible in memory.
 337  */
 338 static bool cramfs_last_page_is_shared(struct inode *inode)
 339 {
 340         struct cramfs_sb_info *sbi = CRAMFS_SB(inode->i_sb);
 341         u32 partial, last_page, blockaddr, *blockptrs;
 342         char *tail_data;
 343 
 344         partial = offset_in_page(inode->i_size);
 345         if (!partial)
 346                 return false;
 347         last_page = inode->i_size >> PAGE_SHIFT;
 348         blockptrs = (u32 *)(sbi->linear_virt_addr + OFFSET(inode));
 349         blockaddr = blockptrs[last_page] & ~CRAMFS_BLK_FLAGS;
 350         blockaddr <<= CRAMFS_BLK_DIRECT_PTR_SHIFT;
 351         tail_data = sbi->linear_virt_addr + blockaddr + partial;
 352         return memchr_inv(tail_data, 0, PAGE_SIZE - partial) ? true : false;
 353 }
 354 
 355 static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
 356 {
 357         struct inode *inode = file_inode(file);
 358         struct cramfs_sb_info *sbi = CRAMFS_SB(inode->i_sb);
 359         unsigned int pages, max_pages, offset;
 360         unsigned long address, pgoff = vma->vm_pgoff;
 361         char *bailout_reason;
 362         int ret;
 363 
 364         ret = generic_file_readonly_mmap(file, vma);
 365         if (ret)
 366                 return ret;
 367 
 368         /*
 369          * Now try to pre-populate ptes for this vma with a direct
 370          * mapping avoiding memory allocation when possible.
 371          */
 372 
 373         /* Could COW work here? */
 374         bailout_reason = "vma is writable";
 375         if (vma->vm_flags & VM_WRITE)
 376                 goto bailout;
 377 
 378         max_pages = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 379         bailout_reason = "beyond file limit";
 380         if (pgoff >= max_pages)
 381                 goto bailout;
 382         pages = min(vma_pages(vma), max_pages - pgoff);
 383 
 384         offset = cramfs_get_block_range(inode, pgoff, &pages);
 385         bailout_reason = "unsuitable block layout";
 386         if (!offset)
 387                 goto bailout;
 388         address = sbi->linear_phys_addr + offset;
 389         bailout_reason = "data is not page aligned";
 390         if (!PAGE_ALIGNED(address))
 391                 goto bailout;
 392 
 393         /* Don't map the last page if it contains some other data */
 394         if (pgoff + pages == max_pages && cramfs_last_page_is_shared(inode)) {
 395                 pr_debug("mmap: %s: last page is shared\n",
 396                          file_dentry(file)->d_name.name);
 397                 pages--;
 398         }
 399 
 400         if (!pages) {
 401                 bailout_reason = "no suitable block remaining";
 402                 goto bailout;
 403         }
 404 
 405         if (pages == vma_pages(vma)) {
 406                 /*
 407                  * The entire vma is mappable. remap_pfn_range() will
 408                  * make it distinguishable from a non-direct mapping
 409                  * in /proc/<pid>/maps by substituting the file offset
 410                  * with the actual physical address.
 411                  */
 412                 ret = remap_pfn_range(vma, vma->vm_start, address >> PAGE_SHIFT,
 413                                       pages * PAGE_SIZE, vma->vm_page_prot);
 414         } else {
 415                 /*
 416                  * Let's create a mixed map if we can't map it all.
 417                  * The normal paging machinery will take care of the
 418                  * unpopulated ptes via cramfs_readpage().
 419                  */
 420                 int i;
 421                 vma->vm_flags |= VM_MIXEDMAP;
 422                 for (i = 0; i < pages && !ret; i++) {
 423                         vm_fault_t vmf;
 424                         unsigned long off = i * PAGE_SIZE;
 425                         pfn_t pfn = phys_to_pfn_t(address + off, PFN_DEV);
 426                         vmf = vmf_insert_mixed(vma, vma->vm_start + off, pfn);
 427                         if (vmf & VM_FAULT_ERROR)
 428                                 ret = vm_fault_to_errno(vmf, 0);
 429                 }
 430         }
 431 
 432         if (!ret)
 433                 pr_debug("mapped %s[%lu] at 0x%08lx (%u/%lu pages) "
 434                          "to vma 0x%08lx, page_prot 0x%llx\n",
 435                          file_dentry(file)->d_name.name, pgoff,
 436                          address, pages, vma_pages(vma), vma->vm_start,
 437                          (unsigned long long)pgprot_val(vma->vm_page_prot));
 438         return ret;
 439 
 440 bailout:
 441         pr_debug("%s[%lu]: direct mmap impossible: %s\n",
 442                  file_dentry(file)->d_name.name, pgoff, bailout_reason);
 443         /* Didn't manage any direct map, but normal paging is still possible */
 444         return 0;
 445 }
 446 
 447 #else /* CONFIG_MMU */
 448 
 449 static int cramfs_physmem_mmap(struct file *file, struct vm_area_struct *vma)
 450 {
 451         return vma->vm_flags & (VM_SHARED | VM_MAYSHARE) ? 0 : -ENOSYS;
 452 }
 453 
 454 static unsigned long cramfs_physmem_get_unmapped_area(struct file *file,
 455                         unsigned long addr, unsigned long len,
 456                         unsigned long pgoff, unsigned long flags)
 457 {
 458         struct inode *inode = file_inode(file);
 459         struct super_block *sb = inode->i_sb;
 460         struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
 461         unsigned int pages, block_pages, max_pages, offset;
 462 
 463         pages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 464         max_pages = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 465         if (pgoff >= max_pages || pages > max_pages - pgoff)
 466                 return -EINVAL;
 467         block_pages = pages;
 468         offset = cramfs_get_block_range(inode, pgoff, &block_pages);
 469         if (!offset || block_pages != pages)
 470                 return -ENOSYS;
 471         addr = sbi->linear_phys_addr + offset;
 472         pr_debug("get_unmapped for %s ofs %#lx siz %lu at 0x%08lx\n",
 473                  file_dentry(file)->d_name.name, pgoff*PAGE_SIZE, len, addr);
 474         return addr;
 475 }
 476 
 477 static unsigned int cramfs_physmem_mmap_capabilities(struct file *file)
 478 {
 479         return NOMMU_MAP_COPY | NOMMU_MAP_DIRECT |
 480                NOMMU_MAP_READ | NOMMU_MAP_EXEC;
 481 }
 482 
 483 #endif /* CONFIG_MMU */
 484 
 485 static const struct file_operations cramfs_physmem_fops = {
 486         .llseek                 = generic_file_llseek,
 487         .read_iter              = generic_file_read_iter,
 488         .splice_read            = generic_file_splice_read,
 489         .mmap                   = cramfs_physmem_mmap,
 490 #ifndef CONFIG_MMU
 491         .get_unmapped_area      = cramfs_physmem_get_unmapped_area,
 492         .mmap_capabilities      = cramfs_physmem_mmap_capabilities,
 493 #endif
 494 };
 495 
 496 static void cramfs_kill_sb(struct super_block *sb)
 497 {
 498         struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
 499 
 500         if (IS_ENABLED(CONFIG_CRAMFS_MTD) && sb->s_mtd) {
 501                 if (sbi && sbi->mtd_point_size)
 502                         mtd_unpoint(sb->s_mtd, 0, sbi->mtd_point_size);
 503                 kill_mtd_super(sb);
 504         } else if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV) && sb->s_bdev) {
 505                 kill_block_super(sb);
 506         }
 507         kfree(sbi);
 508 }
 509 
 510 static int cramfs_reconfigure(struct fs_context *fc)
 511 {
 512         sync_filesystem(fc->root->d_sb);
 513         fc->sb_flags |= SB_RDONLY;
 514         return 0;
 515 }
 516 
 517 static int cramfs_read_super(struct super_block *sb, struct fs_context *fc,
 518                              struct cramfs_super *super)
 519 {
 520         struct cramfs_sb_info *sbi = CRAMFS_SB(sb);
 521         unsigned long root_offset;
 522         bool silent = fc->sb_flags & SB_SILENT;
 523 
 524         /* We don't know the real size yet */
 525         sbi->size = PAGE_SIZE;
 526 
 527         /* Read the first block and get the superblock from it */
 528         mutex_lock(&read_mutex);
 529         memcpy(super, cramfs_read(sb, 0, sizeof(*super)), sizeof(*super));
 530         mutex_unlock(&read_mutex);
 531 
 532         /* Do sanity checks on the superblock */
 533         if (super->magic != CRAMFS_MAGIC) {
 534                 /* check for wrong endianness */
 535                 if (super->magic == CRAMFS_MAGIC_WEND) {
 536                         if (!silent)
 537                                 errorf(fc, "cramfs: wrong endianness");
 538                         return -EINVAL;
 539                 }
 540 
 541                 /* check at 512 byte offset */
 542                 mutex_lock(&read_mutex);
 543                 memcpy(super,
 544                        cramfs_read(sb, 512, sizeof(*super)),
 545                        sizeof(*super));
 546                 mutex_unlock(&read_mutex);
 547                 if (super->magic != CRAMFS_MAGIC) {
 548                         if (super->magic == CRAMFS_MAGIC_WEND && !silent)
 549                                 errorf(fc, "cramfs: wrong endianness");
 550                         else if (!silent)
 551                                 errorf(fc, "cramfs: wrong magic");
 552                         return -EINVAL;
 553                 }
 554         }
 555 
 556         /* get feature flags first */
 557         if (super->flags & ~CRAMFS_SUPPORTED_FLAGS) {
 558                 errorf(fc, "cramfs: unsupported filesystem features");
 559                 return -EINVAL;
 560         }
 561 
 562         /* Check that the root inode is in a sane state */
 563         if (!S_ISDIR(super->root.mode)) {
 564                 errorf(fc, "cramfs: root is not a directory");
 565                 return -EINVAL;
 566         }
 567         /* correct strange, hard-coded permissions of mkcramfs */
 568         super->root.mode |= 0555;
 569 
 570         root_offset = super->root.offset << 2;
 571         if (super->flags & CRAMFS_FLAG_FSID_VERSION_2) {
 572                 sbi->size = super->size;
 573                 sbi->blocks = super->fsid.blocks;
 574                 sbi->files = super->fsid.files;
 575         } else {
 576                 sbi->size = 1<<28;
 577                 sbi->blocks = 0;
 578                 sbi->files = 0;
 579         }
 580         sbi->magic = super->magic;
 581         sbi->flags = super->flags;
 582         if (root_offset == 0)
 583                 infof(fc, "cramfs: empty filesystem");
 584         else if (!(super->flags & CRAMFS_FLAG_SHIFTED_ROOT_OFFSET) &&
 585                  ((root_offset != sizeof(struct cramfs_super)) &&
 586                   (root_offset != 512 + sizeof(struct cramfs_super))))
 587         {
 588                 errorf(fc, "cramfs: bad root offset %lu", root_offset);
 589                 return -EINVAL;
 590         }
 591 
 592         return 0;
 593 }
 594 
 595 static int cramfs_finalize_super(struct super_block *sb,
 596                                  struct cramfs_inode *cramfs_root)
 597 {
 598         struct inode *root;
 599 
 600         /* Set it all up.. */
 601         sb->s_flags |= SB_RDONLY;
 602         sb->s_time_min = 0;
 603         sb->s_time_max = 0;
 604         sb->s_op = &cramfs_ops;
 605         root = get_cramfs_inode(sb, cramfs_root, 0);
 606         if (IS_ERR(root))
 607                 return PTR_ERR(root);
 608         sb->s_root = d_make_root(root);
 609         if (!sb->s_root)
 610                 return -ENOMEM;
 611         return 0;
 612 }
 613 
 614 static int cramfs_blkdev_fill_super(struct super_block *sb, struct fs_context *fc)
 615 {
 616         struct cramfs_sb_info *sbi;
 617         struct cramfs_super super;
 618         int i, err;
 619 
 620         sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
 621         if (!sbi)
 622                 return -ENOMEM;
 623         sb->s_fs_info = sbi;
 624 
 625         /* Invalidate the read buffers on mount: think disk change.. */
 626         for (i = 0; i < READ_BUFFERS; i++)
 627                 buffer_blocknr[i] = -1;
 628 
 629         err = cramfs_read_super(sb, fc, &super);
 630         if (err)
 631                 return err;
 632         return cramfs_finalize_super(sb, &super.root);
 633 }
 634 
 635 static int cramfs_mtd_fill_super(struct super_block *sb, struct fs_context *fc)
 636 {
 637         struct cramfs_sb_info *sbi;
 638         struct cramfs_super super;
 639         int err;
 640 
 641         sbi = kzalloc(sizeof(struct cramfs_sb_info), GFP_KERNEL);
 642         if (!sbi)
 643                 return -ENOMEM;
 644         sb->s_fs_info = sbi;
 645 
 646         /* Map only one page for now.  Will remap it when fs size is known. */
 647         err = mtd_point(sb->s_mtd, 0, PAGE_SIZE, &sbi->mtd_point_size,
 648                         &sbi->linear_virt_addr, &sbi->linear_phys_addr);
 649         if (err || sbi->mtd_point_size != PAGE_SIZE) {
 650                 pr_err("unable to get direct memory access to mtd:%s\n",
 651                        sb->s_mtd->name);
 652                 return err ? : -ENODATA;
 653         }
 654 
 655         pr_info("checking physical address %pap for linear cramfs image\n",
 656                 &sbi->linear_phys_addr);
 657         err = cramfs_read_super(sb, fc, &super);
 658         if (err)
 659                 return err;
 660 
 661         /* Remap the whole filesystem now */
 662         pr_info("linear cramfs image on mtd:%s appears to be %lu KB in size\n",
 663                 sb->s_mtd->name, sbi->size/1024);
 664         mtd_unpoint(sb->s_mtd, 0, PAGE_SIZE);
 665         err = mtd_point(sb->s_mtd, 0, sbi->size, &sbi->mtd_point_size,
 666                         &sbi->linear_virt_addr, &sbi->linear_phys_addr);
 667         if (err || sbi->mtd_point_size != sbi->size) {
 668                 pr_err("unable to get direct memory access to mtd:%s\n",
 669                        sb->s_mtd->name);
 670                 return err ? : -ENODATA;
 671         }
 672 
 673         return cramfs_finalize_super(sb, &super.root);
 674 }
 675 
 676 static int cramfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 677 {
 678         struct super_block *sb = dentry->d_sb;
 679         u64 id = 0;
 680 
 681         if (sb->s_bdev)
 682                 id = huge_encode_dev(sb->s_bdev->bd_dev);
 683         else if (sb->s_dev)
 684                 id = huge_encode_dev(sb->s_dev);
 685 
 686         buf->f_type = CRAMFS_MAGIC;
 687         buf->f_bsize = PAGE_SIZE;
 688         buf->f_blocks = CRAMFS_SB(sb)->blocks;
 689         buf->f_bfree = 0;
 690         buf->f_bavail = 0;
 691         buf->f_files = CRAMFS_SB(sb)->files;
 692         buf->f_ffree = 0;
 693         buf->f_fsid.val[0] = (u32)id;
 694         buf->f_fsid.val[1] = (u32)(id >> 32);
 695         buf->f_namelen = CRAMFS_MAXPATHLEN;
 696         return 0;
 697 }
 698 
 699 /*
 700  * Read a cramfs directory entry.
 701  */
 702 static int cramfs_readdir(struct file *file, struct dir_context *ctx)
 703 {
 704         struct inode *inode = file_inode(file);
 705         struct super_block *sb = inode->i_sb;
 706         char *buf;
 707         unsigned int offset;
 708 
 709         /* Offset within the thing. */
 710         if (ctx->pos >= inode->i_size)
 711                 return 0;
 712         offset = ctx->pos;
 713         /* Directory entries are always 4-byte aligned */
 714         if (offset & 3)
 715                 return -EINVAL;
 716 
 717         buf = kmalloc(CRAMFS_MAXPATHLEN, GFP_KERNEL);
 718         if (!buf)
 719                 return -ENOMEM;
 720 
 721         while (offset < inode->i_size) {
 722                 struct cramfs_inode *de;
 723                 unsigned long nextoffset;
 724                 char *name;
 725                 ino_t ino;
 726                 umode_t mode;
 727                 int namelen;
 728 
 729                 mutex_lock(&read_mutex);
 730                 de = cramfs_read(sb, OFFSET(inode) + offset, sizeof(*de)+CRAMFS_MAXPATHLEN);
 731                 name = (char *)(de+1);
 732 
 733                 /*
 734                  * Namelengths on disk are shifted by two
 735                  * and the name padded out to 4-byte boundaries
 736                  * with zeroes.
 737                  */
 738                 namelen = de->namelen << 2;
 739                 memcpy(buf, name, namelen);
 740                 ino = cramino(de, OFFSET(inode) + offset);
 741                 mode = de->mode;
 742                 mutex_unlock(&read_mutex);
 743                 nextoffset = offset + sizeof(*de) + namelen;
 744                 for (;;) {
 745                         if (!namelen) {
 746                                 kfree(buf);
 747                                 return -EIO;
 748                         }
 749                         if (buf[namelen-1])
 750                                 break;
 751                         namelen--;
 752                 }
 753                 if (!dir_emit(ctx, buf, namelen, ino, mode >> 12))
 754                         break;
 755 
 756                 ctx->pos = offset = nextoffset;
 757         }
 758         kfree(buf);
 759         return 0;
 760 }
 761 
 762 /*
 763  * Lookup and fill in the inode data..
 764  */
 765 static struct dentry *cramfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
 766 {
 767         unsigned int offset = 0;
 768         struct inode *inode = NULL;
 769         int sorted;
 770 
 771         mutex_lock(&read_mutex);
 772         sorted = CRAMFS_SB(dir->i_sb)->flags & CRAMFS_FLAG_SORTED_DIRS;
 773         while (offset < dir->i_size) {
 774                 struct cramfs_inode *de;
 775                 char *name;
 776                 int namelen, retval;
 777                 int dir_off = OFFSET(dir) + offset;
 778 
 779                 de = cramfs_read(dir->i_sb, dir_off, sizeof(*de)+CRAMFS_MAXPATHLEN);
 780                 name = (char *)(de+1);
 781 
 782                 /* Try to take advantage of sorted directories */
 783                 if (sorted && (dentry->d_name.name[0] < name[0]))
 784                         break;
 785 
 786                 namelen = de->namelen << 2;
 787                 offset += sizeof(*de) + namelen;
 788 
 789                 /* Quick check that the name is roughly the right length */
 790                 if (((dentry->d_name.len + 3) & ~3) != namelen)
 791                         continue;
 792 
 793                 for (;;) {
 794                         if (!namelen) {
 795                                 inode = ERR_PTR(-EIO);
 796                                 goto out;
 797                         }
 798                         if (name[namelen-1])
 799                                 break;
 800                         namelen--;
 801                 }
 802                 if (namelen != dentry->d_name.len)
 803                         continue;
 804                 retval = memcmp(dentry->d_name.name, name, namelen);
 805                 if (retval > 0)
 806                         continue;
 807                 if (!retval) {
 808                         inode = get_cramfs_inode(dir->i_sb, de, dir_off);
 809                         break;
 810                 }
 811                 /* else (retval < 0) */
 812                 if (sorted)
 813                         break;
 814         }
 815 out:
 816         mutex_unlock(&read_mutex);
 817         return d_splice_alias(inode, dentry);
 818 }
 819 
 820 static int cramfs_readpage(struct file *file, struct page *page)
 821 {
 822         struct inode *inode = page->mapping->host;
 823         u32 maxblock;
 824         int bytes_filled;
 825         void *pgdata;
 826 
 827         maxblock = (inode->i_size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 828         bytes_filled = 0;
 829         pgdata = kmap(page);
 830 
 831         if (page->index < maxblock) {
 832                 struct super_block *sb = inode->i_sb;
 833                 u32 blkptr_offset = OFFSET(inode) + page->index * 4;
 834                 u32 block_ptr, block_start, block_len;
 835                 bool uncompressed, direct;
 836 
 837                 mutex_lock(&read_mutex);
 838                 block_ptr = *(u32 *) cramfs_read(sb, blkptr_offset, 4);
 839                 uncompressed = (block_ptr & CRAMFS_BLK_FLAG_UNCOMPRESSED);
 840                 direct = (block_ptr & CRAMFS_BLK_FLAG_DIRECT_PTR);
 841                 block_ptr &= ~CRAMFS_BLK_FLAGS;
 842 
 843                 if (direct) {
 844                         /*
 845                          * The block pointer is an absolute start pointer,
 846                          * shifted by 2 bits. The size is included in the
 847                          * first 2 bytes of the data block when compressed,
 848                          * or PAGE_SIZE otherwise.
 849                          */
 850                         block_start = block_ptr << CRAMFS_BLK_DIRECT_PTR_SHIFT;
 851                         if (uncompressed) {
 852                                 block_len = PAGE_SIZE;
 853                                 /* if last block: cap to file length */
 854                                 if (page->index == maxblock - 1)
 855                                         block_len =
 856                                                 offset_in_page(inode->i_size);
 857                         } else {
 858                                 block_len = *(u16 *)
 859                                         cramfs_read(sb, block_start, 2);
 860                                 block_start += 2;
 861                         }
 862                 } else {
 863                         /*
 864                          * The block pointer indicates one past the end of
 865                          * the current block (start of next block). If this
 866                          * is the first block then it starts where the block
 867                          * pointer table ends, otherwise its start comes
 868                          * from the previous block's pointer.
 869                          */
 870                         block_start = OFFSET(inode) + maxblock * 4;
 871                         if (page->index)
 872                                 block_start = *(u32 *)
 873                                         cramfs_read(sb, blkptr_offset - 4, 4);
 874                         /* Beware... previous ptr might be a direct ptr */
 875                         if (unlikely(block_start & CRAMFS_BLK_FLAG_DIRECT_PTR)) {
 876                                 /* See comments on earlier code. */
 877                                 u32 prev_start = block_start;
 878                                 block_start = prev_start & ~CRAMFS_BLK_FLAGS;
 879                                 block_start <<= CRAMFS_BLK_DIRECT_PTR_SHIFT;
 880                                 if (prev_start & CRAMFS_BLK_FLAG_UNCOMPRESSED) {
 881                                         block_start += PAGE_SIZE;
 882                                 } else {
 883                                         block_len = *(u16 *)
 884                                                 cramfs_read(sb, block_start, 2);
 885                                         block_start += 2 + block_len;
 886                                 }
 887                         }
 888                         block_start &= ~CRAMFS_BLK_FLAGS;
 889                         block_len = block_ptr - block_start;
 890                 }
 891 
 892                 if (block_len == 0)
 893                         ; /* hole */
 894                 else if (unlikely(block_len > 2*PAGE_SIZE ||
 895                                   (uncompressed && block_len > PAGE_SIZE))) {
 896                         mutex_unlock(&read_mutex);
 897                         pr_err("bad data blocksize %u\n", block_len);
 898                         goto err;
 899                 } else if (uncompressed) {
 900                         memcpy(pgdata,
 901                                cramfs_read(sb, block_start, block_len),
 902                                block_len);
 903                         bytes_filled = block_len;
 904                 } else {
 905                         bytes_filled = cramfs_uncompress_block(pgdata,
 906                                  PAGE_SIZE,
 907                                  cramfs_read(sb, block_start, block_len),
 908                                  block_len);
 909                 }
 910                 mutex_unlock(&read_mutex);
 911                 if (unlikely(bytes_filled < 0))
 912                         goto err;
 913         }
 914 
 915         memset(pgdata + bytes_filled, 0, PAGE_SIZE - bytes_filled);
 916         flush_dcache_page(page);
 917         kunmap(page);
 918         SetPageUptodate(page);
 919         unlock_page(page);
 920         return 0;
 921 
 922 err:
 923         kunmap(page);
 924         ClearPageUptodate(page);
 925         SetPageError(page);
 926         unlock_page(page);
 927         return 0;
 928 }
 929 
 930 static const struct address_space_operations cramfs_aops = {
 931         .readpage = cramfs_readpage
 932 };
 933 
 934 /*
 935  * Our operations:
 936  */
 937 
 938 /*
 939  * A directory can only readdir
 940  */
 941 static const struct file_operations cramfs_directory_operations = {
 942         .llseek         = generic_file_llseek,
 943         .read           = generic_read_dir,
 944         .iterate_shared = cramfs_readdir,
 945 };
 946 
 947 static const struct inode_operations cramfs_dir_inode_operations = {
 948         .lookup         = cramfs_lookup,
 949 };
 950 
 951 static const struct super_operations cramfs_ops = {
 952         .statfs         = cramfs_statfs,
 953 };
 954 
 955 static int cramfs_get_tree(struct fs_context *fc)
 956 {
 957         int ret = -ENOPROTOOPT;
 958 
 959         if (IS_ENABLED(CONFIG_CRAMFS_MTD)) {
 960                 ret = get_tree_mtd(fc, cramfs_mtd_fill_super);
 961                 if (!ret)
 962                         return 0;
 963         }
 964         if (IS_ENABLED(CONFIG_CRAMFS_BLOCKDEV))
 965                 ret = get_tree_bdev(fc, cramfs_blkdev_fill_super);
 966         return ret;
 967 }
 968 
 969 static const struct fs_context_operations cramfs_context_ops = {
 970         .get_tree       = cramfs_get_tree,
 971         .reconfigure    = cramfs_reconfigure,
 972 };
 973 
 974 /*
 975  * Set up the filesystem mount context.
 976  */
 977 static int cramfs_init_fs_context(struct fs_context *fc)
 978 {
 979         fc->ops = &cramfs_context_ops;
 980         return 0;
 981 }
 982 
 983 static struct file_system_type cramfs_fs_type = {
 984         .owner          = THIS_MODULE,
 985         .name           = "cramfs",
 986         .init_fs_context = cramfs_init_fs_context,
 987         .kill_sb        = cramfs_kill_sb,
 988         .fs_flags       = FS_REQUIRES_DEV,
 989 };
 990 MODULE_ALIAS_FS("cramfs");
 991 
 992 static int __init init_cramfs_fs(void)
 993 {
 994         int rv;
 995 
 996         rv = cramfs_uncompress_init();
 997         if (rv < 0)
 998                 return rv;
 999         rv = register_filesystem(&cramfs_fs_type);
1000         if (rv < 0)
1001                 cramfs_uncompress_exit();
1002         return rv;
1003 }
1004 
1005 static void __exit exit_cramfs_fs(void)
1006 {
1007         cramfs_uncompress_exit();
1008         unregister_filesystem(&cramfs_fs_type);
1009 }
1010 
1011 module_init(init_cramfs_fs)
1012 module_exit(exit_cramfs_fs)
1013 MODULE_LICENSE("GPL");
/* [<][>][^][v][top][bottom][index][help] */
root/fs/cramfs/inode.c

DEFINITIONS
