/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ #ifndef _UAPI__CRAMFS_H #define _UAPI__CRAMFS_H
#include <linux/types.h> #include <linux/magic.h>
#define CRAMFS_SIGNATURE "Compressed ROMFS"
/* * Width of various bitfields in struct cramfs_inode. * Primarily used to generate warnings in mkcramfs.
*/ #define CRAMFS_MODE_WIDTH 16 #define CRAMFS_UID_WIDTH 16 #define CRAMFS_SIZE_WIDTH 24 #define CRAMFS_GID_WIDTH 8 #define CRAMFS_NAMELEN_WIDTH 6 #define CRAMFS_OFFSET_WIDTH 26
/* * Since inode.namelen is a unsigned 6-bit number, the maximum cramfs * path length is 63 << 2 = 252.
*/ #define CRAMFS_MAXPATHLEN (((1 << CRAMFS_NAMELEN_WIDTH) - 1) << 2)
/* * Reasonably terse representation of the inode data.
*/ struct cramfs_inode {
__u32 mode:CRAMFS_MODE_WIDTH, uid:CRAMFS_UID_WIDTH; /* SIZE for device files is i_rdev */
__u32 size:CRAMFS_SIZE_WIDTH, gid:CRAMFS_GID_WIDTH; /* NAMELEN is the length of the file name, divided by 4 and
rounded up. (cramfs doesn't support hard links.) */ /* OFFSET: For symlinks and non-empty regular files, this contains the offset (divided by 4) of the file data in compressed form (starting with an array of block pointers; see README). For non-empty directories it is the offset (divided by 4) of the inode of the first file in that
directory. For anything else, offset is zero. */
__u32 namelen:CRAMFS_NAMELEN_WIDTH, offset:CRAMFS_OFFSET_WIDTH;
};
/* * Superblock information at the beginning of the FS.
*/ struct cramfs_super {
__u32 magic; /* 0x28cd3d45 - random number */
__u32 size; /* length in bytes */
__u32 flags; /* feature flags */
__u32 future; /* reserved for future use */
__u8 signature[16]; /* "Compressed ROMFS" */ struct cramfs_info fsid; /* unique filesystem info */
__u8 name[16]; /* user-defined name */ struct cramfs_inode root; /* root inode data */
};
/* * Feature flags * * 0x00000000 - 0x000000ff: features that work for all past kernels * 0x00000100 - 0xffffffff: features that don't work for past kernels
*/ #define CRAMFS_FLAG_FSID_VERSION_2 0x00000001 /* fsid version #2 */ #define CRAMFS_FLAG_SORTED_DIRS 0x00000002 /* sorted dirs */ #define CRAMFS_FLAG_HOLES 0x00000100 /* support for holes */ #define CRAMFS_FLAG_WRONG_SIGNATURE 0x00000200 /* reserved */ #define CRAMFS_FLAG_SHIFTED_ROOT_OFFSET 0x00000400 /* shifted root fs */ #define CRAMFS_FLAG_EXT_BLOCK_POINTERS 0x00000800 /* block pointer extensions */
/* * Valid values in super.flags. Currently we refuse to mount * if (flags & ~CRAMFS_SUPPORTED_FLAGS). Maybe that should be * changed to test super.future instead.
*/ #define CRAMFS_SUPPORTED_FLAGS ( 0x000000ff \
| CRAMFS_FLAG_HOLES \
| CRAMFS_FLAG_WRONG_SIGNATURE \
| CRAMFS_FLAG_SHIFTED_ROOT_OFFSET \
| CRAMFS_FLAG_EXT_BLOCK_POINTERS )
/* * Block pointer flags * * The maximum block offset that needs to be represented is roughly: * * (1 << CRAMFS_OFFSET_WIDTH) * 4 + * (1 << CRAMFS_SIZE_WIDTH) / PAGE_SIZE * (4 + PAGE_SIZE) * = 0x11004000 * * That leaves room for 3 flag bits in the block pointer table.
*/ #define CRAMFS_BLK_FLAG_UNCOMPRESSED (1 << 31) #define CRAMFS_BLK_FLAG_DIRECT_PTR (1 << 30)
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