diff options
Diffstat (limited to 'include/uapi/linux/cramfs_fs.h')
| -rw-r--r-- | include/uapi/linux/cramfs_fs.h | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/include/uapi/linux/cramfs_fs.h b/include/uapi/linux/cramfs_fs.h new file mode 100644 index 000000000..6713669aa --- /dev/null +++ b/include/uapi/linux/cramfs_fs.h @@ -0,0 +1,113 @@ +/* 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; +}; + +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 /* _UAPI__CRAMFS_H */ |