LXR linux/include/uapi/linux/cramfs

   1/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
   2#ifndef _UAPI__CRAMFS_H
   3#define _UAPI__CRAMFS_H
   4
   5#include <linux/types.h>
   6#include <linux/magic.h>
   7
   8#define CRAMFS_SIGNATURE        "Compressed ROMFS"
   9
  10/*
  11 * Width of various bitfields in struct cramfs_inode.
  12 * Primarily used to generate warnings in mkcramfs.
  13 */
  14#define CRAMFS_MODE_WIDTH 16
  15#define CRAMFS_UID_WIDTH 16
  16#define CRAMFS_SIZE_WIDTH 24
  17#define CRAMFS_GID_WIDTH 8
  18#define CRAMFS_NAMELEN_WIDTH 6
  19#define CRAMFS_OFFSET_WIDTH 26
  20
  21/*
  22 * Since inode.namelen is a unsigned 6-bit number, the maximum cramfs
  23 * path length is 63 << 2 = 252.
  24 */
  25#define CRAMFS_MAXPATHLEN (((1 << CRAMFS_NAMELEN_WIDTH) - 1) << 2)
  26
  27/*
  28 * Reasonably terse representation of the inode data.
  29 */
  30struct cramfs_inode {
  31        __u32 mode:CRAMFS_MODE_WIDTH, uid:CRAMFS_UID_WIDTH;
  32        /* SIZE for device files is i_rdev */
  33        __u32 size:CRAMFS_SIZE_WIDTH, gid:CRAMFS_GID_WIDTH;
  34        /* NAMELEN is the length of the file name, divided by 4 and
  35           rounded up.  (cramfs doesn't support hard links.) */
  36        /* OFFSET: For symlinks and non-empty regular files, this
  37           contains the offset (divided by 4) of the file data in
  38           compressed form (starting with an array of block pointers;
  39           see README).  For non-empty directories it is the offset
  40           (divided by 4) of the inode of the first file in that
  41           directory.  For anything else, offset is zero. */
  42        __u32 namelen:CRAMFS_NAMELEN_WIDTH, offset:CRAMFS_OFFSET_WIDTH;
  43};
  44
  45struct cramfs_info {
  46        __u32 crc;
  47        __u32 edition;
  48        __u32 blocks;
  49        __u32 files;
  50};
  51
  52/*
  53 * Superblock information at the beginning of the FS.
  54 */
  55struct cramfs_super {
  56        __u32 magic;                    /* 0x28cd3d45 - random number */
  57        __u32 size;                     /* length in bytes */
  58        __u32 flags;                    /* feature flags */
  59        __u32 future;                   /* reserved for future use */
  60        __u8 signature[16];             /* "Compressed ROMFS" */
  61        struct cramfs_info fsid;        /* unique filesystem info */
  62        __u8 name[16];                  /* user-defined name */
  63        struct cramfs_inode root;       /* root inode data */
  64};
  65
  66/*
  67 * Feature flags
  68 *
  69 * 0x00000000 - 0x000000ff: features that work for all past kernels
  70 * 0x00000100 - 0xffffffff: features that don't work for past kernels
  71 */
  72#define CRAMFS_FLAG_FSID_VERSION_2      0x00000001      /* fsid version #2 */
  73#define CRAMFS_FLAG_SORTED_DIRS         0x00000002      /* sorted dirs */
  74#define CRAMFS_FLAG_HOLES               0x00000100      /* support for holes */
  75#define CRAMFS_FLAG_WRONG_SIGNATURE     0x00000200      /* reserved */
  76#define CRAMFS_FLAG_SHIFTED_ROOT_OFFSET 0x00000400      /* shifted root fs */
  77#define CRAMFS_FLAG_EXT_BLOCK_POINTERS  0x00000800      /* block pointer extensions */
  78
  79/*
  80 * Valid values in super.flags.  Currently we refuse to mount
  81 * if (flags & ~CRAMFS_SUPPORTED_FLAGS).  Maybe that should be
  82 * changed to test super.future instead.
  83 */
  84#define CRAMFS_SUPPORTED_FLAGS  ( 0x000000ff \
  85                                | CRAMFS_FLAG_HOLES \
  86                                | CRAMFS_FLAG_WRONG_SIGNATURE \
  87                                | CRAMFS_FLAG_SHIFTED_ROOT_OFFSET \
  88                                | CRAMFS_FLAG_EXT_BLOCK_POINTERS )
  89
  90/*
  91 * Block pointer flags
  92 *
  93 * The maximum block offset that needs to be represented is roughly:
  94 *
  95 *   (1 << CRAMFS_OFFSET_WIDTH) * 4 +
  96 *   (1 << CRAMFS_SIZE_WIDTH) / PAGE_SIZE * (4 + PAGE_SIZE)
  97 *   = 0x11004000
  98 *
  99 * That leaves room for 3 flag bits in the block pointer table.
 100 */
 101#define CRAMFS_BLK_FLAG_UNCOMPRESSED    (1 << 31)
 102#define CRAMFS_BLK_FLAG_DIRECT_PTR      (1 << 30)
 103
 104#define CRAMFS_BLK_FLAGS        ( CRAMFS_BLK_FLAG_UNCOMPRESSED \
 105                                | CRAMFS_BLK_FLAG_DIRECT_PTR )
 106
 107/*
 108 * Direct blocks are at least 4-byte aligned.
 109 * Pointers to direct blocks are shifted down by 2 bits.
 110 */
 111#define CRAMFS_BLK_DIRECT_PTR_SHIFT     2
 112
 113#endif /* _UAPI__CRAMFS_H */
 114