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cramfs_fs.h
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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  */
29 struct cramfs_inode {
31  /* SIZE for device files is i_rdev */
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. */
42 };
43 
44 struct cramfs_info {
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 
88 #endif /* _UAPI__CRAMFS_H */