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