disk-utils/cramfs.h

   1 /*
   2  * SPDX-License-Identifier: GPL-2.0-or-later
   3  *
   4  * cramfs_common - cramfs common code
   5  *
   6  * Copyright (c) 2008 Roy Peled, the.roy.peled  -at-  gmail
   7  * Copyright (c) 2004-2006 by Juliane Holzt, kju -at- fqdn.org
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  * GNU General Public License for more details.
  18  */
  19 #ifndef __CRAMFS_H
  20 #define __CRAMFS_H
  21
  22 #include <stdint.h>
  23
  24 #define CRAMFS_MAGIC            0x28cd3d45      /* some random number */
  25 #define CRAMFS_SIGNATURE        "Compressed ROMFS"
  26
  27 /*
  28  * Width of various bitfields in struct cramfs_inode.
  29  * Primarily used to generate warnings in mkcramfs.
  30  */
  31 #define CRAMFS_MODE_WIDTH 16
  32 #define CRAMFS_UID_WIDTH 16
  33 #define CRAMFS_SIZE_WIDTH 24
  34 #define CRAMFS_GID_WIDTH 8
  35 #define CRAMFS_NAMELEN_WIDTH 6
  36 #define CRAMFS_OFFSET_WIDTH 26
  37
  38 #ifndef HOST_IS_BIG_ENDIAN
  39 #define HOST_IS_BIG_ENDIAN (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
  40 #endif
  41
  42 /*
  43  * Reasonably terse representation of the inode data.
  44  */
  45 struct cramfs_inode {
  46         uint32_t mode:16, uid:16;
  47         /* SIZE for device files is i_rdev */
  48         uint32_t size:24, gid:8;
  49         /*
  50          * NAMELEN is the length of the file name, divided by 4 and
  51          * rounded up.  (cramfs doesn't support hard links.)
  52          *
  53          * OFFSET: For symlinks and non-empty regular files, this
  54          * contains the offset (divided by 4) of the file data in
  55          * compressed form (starting with an array of block pointers;
  56          * see README).  For non-empty directories it is the offset
  57          * (divided by 4) of the inode of the first file in that
  58          * directory.  For anything else, offset is zero.
  59          */
  60         uint32_t namelen:6, offset:26;
  61 };
  62
  63 struct cramfs_info {
  64         uint32_t crc;
  65         uint32_t edition;
  66         uint32_t blocks;
  67         uint32_t files;
  68 };
  69
  70 /*
  71  * Superblock information at the beginning of the FS.
  72  */
  73 struct cramfs_super {
  74         uint32_t magic;         /* 0x28cd3d45 - random number */
  75         uint32_t size;          /* Not used.  mkcramfs currently
  76                                    writes a constant 1<<16 here. */
  77         uint32_t flags;         /* 0 */
  78         uint32_t future;                /* 0 */
  79         uint8_t signature[16];  /* "Compressed ROMFS" */
  80         struct cramfs_info fsid;/* unique filesystem info */
  81         uint8_t name[16];               /* user-defined name */
  82         struct cramfs_inode root;       /* Root inode data */
  83 };
  84
  85 #define CRAMFS_FLAG_FSID_VERSION_2      0x00000001      /* fsid version #2 */
  86 #define CRAMFS_FLAG_SORTED_DIRS         0x00000002      /* sorted dirs */
  87 #define CRAMFS_FLAG_HOLES               0x00000100      /* support for holes */
  88 #define CRAMFS_FLAG_WRONG_SIGNATURE     0x00000200      /* reserved */
  89 #define CRAMFS_FLAG_SHIFTED_ROOT_OFFSET 0x00000400      /* shifted root fs */
  90
  91 /*
  92  * Valid values in super.flags.  Currently we refuse to mount
  93  * if (flags & ~CRAMFS_SUPPORTED_FLAGS).  Maybe that should be
  94  * changed to test super.future instead.
  95  */
  96 #define CRAMFS_SUPPORTED_FLAGS (0xff)
  97
  98 /* Uncompression interfaces to the underlying zlib */
  99 int cramfs_uncompress_block(void *dst, int dstlen, void *src, int srclen);
 100 int cramfs_uncompress_init(void);
 101 int cramfs_uncompress_exit(void);
 102
 103 uint32_t u32_toggle_endianness(int big_endian, uint32_t what);
 104 void super_toggle_endianness(int from_big_endian, struct cramfs_super *super);
 105 void inode_to_host(int from_big_endian, struct cramfs_inode *inode_in,
 106                    struct cramfs_inode *inode_out);
 107 void inode_from_host(int to_big_endian, struct cramfs_inode *inode_in,
 108                      struct cramfs_inode *inode_out);
 109
 110 #endif