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