1 #ifndef __CRAMFS_H
2 #define __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  */
29 struct 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 
44 struct 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  */
54 struct 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 #ifdef __KERNEL__
88 /* Uncompression interfaces to the underlying zlib */
89 int cramfs_uncompress_block(void *dst, int dstlen, void *src, int srclen);
90 int cramfs_uncompress_init(void);
91 void cramfs_uncompress_exit(void);
92 #endif /* __KERNEL__ */
93 
94 #endif
95