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 | |