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1/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */2#ifndef _UAPI__CRAMFS_H3#define _UAPI__CRAMFS_H4 5#include <linux/types.h>6#include <linux/magic.h>7 8#define CRAMFS_SIGNATURE "Compressed ROMFS"9 10/*11 * Width of various bitfields in struct cramfs_inode.12 * Primarily used to generate warnings in mkcramfs.13 */14#define CRAMFS_MODE_WIDTH 1615#define CRAMFS_UID_WIDTH 1616#define CRAMFS_SIZE_WIDTH 2417#define CRAMFS_GID_WIDTH 818#define CRAMFS_NAMELEN_WIDTH 619#define CRAMFS_OFFSET_WIDTH 2620 21/*22 * Since inode.namelen is a unsigned 6-bit number, the maximum cramfs23 * path length is 63 << 2 = 252.24 */25#define CRAMFS_MAXPATHLEN (((1 << CRAMFS_NAMELEN_WIDTH) - 1) << 2)26 27/*28 * Reasonably terse representation of the inode data.29 */30struct cramfs_inode {31 __u32 mode:CRAMFS_MODE_WIDTH, uid:CRAMFS_UID_WIDTH;32 /* SIZE for device files is i_rdev */33 __u32 size:CRAMFS_SIZE_WIDTH, gid:CRAMFS_GID_WIDTH;34 /* NAMELEN is the length of the file name, divided by 4 and35 rounded up. (cramfs doesn't support hard links.) */36 /* OFFSET: For symlinks and non-empty regular files, this37 contains the offset (divided by 4) of the file data in38 compressed form (starting with an array of block pointers;39 see README). For non-empty directories it is the offset40 (divided by 4) of the inode of the first file in that41 directory. For anything else, offset is zero. */42 __u32 namelen:CRAMFS_NAMELEN_WIDTH, offset:CRAMFS_OFFSET_WIDTH;43};44 45struct cramfs_info {46 __u32 crc;47 __u32 edition;48 __u32 blocks;49 __u32 files;50};51 52/*53 * Superblock information at the beginning of the FS.54 */55struct cramfs_super {56 __u32 magic; /* 0x28cd3d45 - random number */57 __u32 size; /* length in bytes */58 __u32 flags; /* feature flags */59 __u32 future; /* reserved for future use */60 __u8 signature[16]; /* "Compressed ROMFS" */61 struct cramfs_info fsid; /* unique filesystem info */62 __u8 name[16]; /* user-defined name */63 struct cramfs_inode root; /* root inode data */64};65 66/*67 * Feature flags68 *69 * 0x00000000 - 0x000000ff: features that work for all past kernels70 * 0x00000100 - 0xffffffff: features that don't work for past kernels71 */72#define CRAMFS_FLAG_FSID_VERSION_2 0x00000001 /* fsid version #2 */73#define CRAMFS_FLAG_SORTED_DIRS 0x00000002 /* sorted dirs */74#define CRAMFS_FLAG_HOLES 0x00000100 /* support for holes */75#define CRAMFS_FLAG_WRONG_SIGNATURE 0x00000200 /* reserved */76#define CRAMFS_FLAG_SHIFTED_ROOT_OFFSET 0x00000400 /* shifted root fs */77#define CRAMFS_FLAG_EXT_BLOCK_POINTERS 0x00000800 /* block pointer extensions */78 79/*80 * Valid values in super.flags. Currently we refuse to mount81 * if (flags & ~CRAMFS_SUPPORTED_FLAGS). Maybe that should be82 * changed to test super.future instead.83 */84#define CRAMFS_SUPPORTED_FLAGS ( 0x000000ff \85 | CRAMFS_FLAG_HOLES \86 | CRAMFS_FLAG_WRONG_SIGNATURE \87 | CRAMFS_FLAG_SHIFTED_ROOT_OFFSET \88 | CRAMFS_FLAG_EXT_BLOCK_POINTERS )89 90/*91 * Block pointer flags92 *93 * The maximum block offset that needs to be represented is roughly:94 *95 * (1 << CRAMFS_OFFSET_WIDTH) * 4 +96 * (1 << CRAMFS_SIZE_WIDTH) / PAGE_SIZE * (4 + PAGE_SIZE)97 * = 0x1100400098 *99 * That leaves room for 3 flag bits in the block pointer table.100 */101#define CRAMFS_BLK_FLAG_UNCOMPRESSED (1 << 31)102#define CRAMFS_BLK_FLAG_DIRECT_PTR (1 << 30)103 104#define CRAMFS_BLK_FLAGS ( CRAMFS_BLK_FLAG_UNCOMPRESSED \105 | CRAMFS_BLK_FLAG_DIRECT_PTR )106 107/*108 * Direct blocks are at least 4-byte aligned.109 * Pointers to direct blocks are shifted down by 2 bits.110 */111#define CRAMFS_BLK_DIRECT_PTR_SHIFT 2112 113#endif /* _UAPI__CRAMFS_H */114