fstype/cramfs_fs.h

   1 #ifndef __CRAMFS_H
   2 #define __CRAMFS_H
   3
   4 #define CRAMFS_MAGIC            0x28cd3d45      /* some random number */
   5 #define CRAMFS_SIGNATURE        "Compressed ROMFS"
   6
   7 /*
   8  * Width of various bitfields in struct cramfs_inode.
   9  * Primarily used to generate warnings in mkcramfs.
  10  */
  11 #define CRAMFS_MODE_WIDTH 16
  12 #define CRAMFS_UID_WIDTH 16
  13 #define CRAMFS_SIZE_WIDTH 24
  14 #define CRAMFS_GID_WIDTH 8
  15 #define CRAMFS_NAMELEN_WIDTH 6
  16 #define CRAMFS_OFFSET_WIDTH 26
  17
  18 /*
  19  * Since inode.namelen is a unsigned 6-bit number, the maximum cramfs
  20  * path length is 63 << 2 = 252.
  21  */
  22 #define CRAMFS_MAXPATHLEN (((1 << CRAMFS_NAMELEN_WIDTH) - 1) << 2)
  23
  24 /*
  25  * Reasonably terse representation of the inode data.
  26  */
  27 struct cramfs_inode {
  28         __u32 mode:CRAMFS_MODE_WIDTH, uid:CRAMFS_UID_WIDTH;
  29         /* SIZE for device files is i_rdev */
  30         __u32 size:CRAMFS_SIZE_WIDTH, gid:CRAMFS_GID_WIDTH;
  31         /* NAMELEN is the length of the file name, divided by 4 and
  32            rounded up.  (cramfs doesn't support hard links.) */
  33         /* OFFSET: For symlinks and non-empty regular files, this
  34            contains the offset (divided by 4) of the file data in
  35            compressed form (starting with an array of block pointers;
  36            see README).  For non-empty directories it is the offset
  37            (divided by 4) of the inode of the first file in that
  38            directory.  For anything else, offset is zero. */
  39         __u32 namelen:CRAMFS_NAMELEN_WIDTH, offset:CRAMFS_OFFSET_WIDTH;
  40 };
  41
  42 struct cramfs_info {
  43         __u32 crc;
  44         __u32 edition;
  45         __u32 blocks;
  46         __u32 files;
  47 };
  48
  49 /*
  50  * Superblock information at the beginning of the FS.
  51  */
  52 struct cramfs_super {
  53         __u32 magic;            /* 0x28cd3d45 - random number */
  54         __u32 size;             /* length in bytes */
  55         __u32 flags;            /* feature flags */
  56         __u32 future;           /* reserved for future use */
  57         __u8 signature[16];     /* "Compressed ROMFS" */
  58         struct cramfs_info fsid;        /* unique filesystem info */
  59         __u8 name[16];          /* user-defined name */
  60         struct cramfs_inode root;       /* root inode data */
  61 };
  62
  63 /*
  64  * Feature flags
  65  *
  66  * 0x00000000 - 0x000000ff: features that work for all past kernels
  67  * 0x00000100 - 0xffffffff: features that don't work for past kernels
  68  */
  69 #define CRAMFS_FLAG_FSID_VERSION_2      0x00000001      /* fsid version #2 */
  70 #define CRAMFS_FLAG_SORTED_DIRS         0x00000002      /* sorted dirs */
  71 #define CRAMFS_FLAG_HOLES               0x00000100      /* support for holes */
  72 #define CRAMFS_FLAG_WRONG_SIGNATURE     0x00000200      /* reserved */
  73 #define CRAMFS_FLAG_SHIFTED_ROOT_OFFSET 0x00000400      /* shifted root fs */
  74
  75 /*
  76  * Valid values in super.flags.  Currently we refuse to mount
  77  * if (flags & ~CRAMFS_SUPPORTED_FLAGS).  Maybe that should be
  78  * changed to test super.future instead.
  79  */
  80 #define CRAMFS_SUPPORTED_FLAGS  ( 0x000000ff \
  81                                 | CRAMFS_FLAG_HOLES \
  82                                 | CRAMFS_FLAG_WRONG_SIGNATURE \
  83                                 | CRAMFS_FLAG_SHIFTED_ROOT_OFFSET )
  84
  85 #endif