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 */ 30 struct 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 45 struct 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 */ 55 struct 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