/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ #ifndef __CRAMFS_H #define __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; }; struct cramfs_info { __u32 crc; __u32 edition; __u32 blocks; __u32 files; }; /* * 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) #define CRAMFS_BLK_FLAGS ( CRAMFS_BLK_FLAG_UNCOMPRESSED \ | CRAMFS_BLK_FLAG_DIRECT_PTR ) /* * Direct blocks are at least 4-byte aligned. * Pointers to direct blocks are shifted down by 2 bits. */ #define CRAMFS_BLK_DIRECT_PTR_SHIFT 2 #endif /* __CRAMFS_H */