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CloverBootloader/Ext4Pkg/Ext4Dxe/Ext4Disk.h

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/** @file
Raw filesystem data structures
Copyright (c) 2021 - 2023 Pedro Falcato All rights reserved.
SPDX-License-Identifier: BSD-2-Clause-Patent
Layout of an EXT2/3/4 filesystem:
(note: this driver has been developed using
https://www.kernel.org/doc/html/latest/filesystems/ext4/index.html as
documentation).
An ext2/3/4 filesystem (here on out referred to as simply an ext4 filesystem,
due to the similarities) is composed of various concepts:
1) Superblock
The superblock is the structure near (1024 bytes offset from the start)
the start of the partition, and describes the filesystem in general.
Here, we get to know the size of the filesystem's blocks, which features
it supports or not, whether it's been cleanly unmounted, how many blocks
we have, etc.
2) Block groups
EXT4 filesystems are divided into block groups, and each block group covers
s_blocks_per_group(8 * Block Size) blocks. Each block group has an
associated block group descriptor; these are present directly after the
superblock. Each block group descriptor contains the location of the
inode table, and the inode and block bitmaps (note these bitmaps are only
a block long, which gets us the 8 * Block Size formula covered previously).
3) Blocks
The ext4 filesystem is divided in blocks, of size s_log_block_size ^ 1024.
Blocks can be allocated using individual block groups's bitmaps. Note
that block 0 is invalid and its presence on extents/block tables means
it's part of a file hole, and that particular location must be read as
a block full of zeros.
4) Inodes
The ext4 filesystem divides files/directories into inodes (originally
index nodes). Each file/socket/symlink/directory/etc (here on out referred
to as a file, since there is no distinction under the ext4 filesystem) is
stored as a /nameless/ inode, that is stored in some block group's inode
table. Each inode has s_inode_size size (or GOOD_OLD_INODE_SIZE if it's
an old filesystem), and holds various metadata about the file. Since the
largest inode structure right now is ~160 bytes, the rest of the inode
contains inline extended attributes. Inodes' data is stored using either
data blocks (under ext2/3) or extents (under ext4).
5) Extents
Ext4 inodes store data in extents. These let N contiguous logical blocks
that are represented by N contiguous physical blocks be represented by a
single extent structure, which minimizes filesystem metadata bloat and
speeds up block mapping (particularly due to the fact that high-quality
ext4 implementations like linux's try /really/ hard to make the file
contiguous, so it's common to have files with almost 0 fragmentation).
Inodes that use extents store them in a tree, and the top of the tree
is stored on i_data. The tree's leaves always start with an
EXT4_EXTENT_HEADER and contain EXT4_EXTENT_INDEX on eh_depth != 0 and
EXT4_EXTENT on eh_depth = 0; these entries are always sorted by logical
block.
6) Directories
Ext4 directories are files that store name -> inode mappings for the
logical directory; this is where files get their names, which means ext4
inodes do not themselves have names, since they can be linked (present)
multiple times with different names. Directories can store entries in two
different ways:
1) Classical linear directories: They store entries as a mostly-linked
mostly-list of EXT4_DIR_ENTRY.
2) Hash tree directories: These are used for larger directories, with
hundreds of entries, and are designed in a backwards compatible way.
These are not yet implemented in the Ext4Dxe driver.
7) Journal
Ext3/4 filesystems have a journal to help protect the filesystem against
system crashes. This is not yet implemented in Ext4Dxe but is described
in detail in the Linux kernel's documentation.
**/
#ifndef EXT4_DISK_H_
#define EXT4_DISK_H_
#include <Uefi.h>
#define EXT4_SUPERBLOCK_OFFSET 1024U
#define EXT4_SIGNATURE 0xEF53U
#define EXT4_FS_STATE_UNMOUNTED 0x1
#define EXT4_FS_STATE_ERRORS_DETECTED 0x2
#define EXT4_FS_STATE_RECOVERING_ORPHANS 0x4
#define EXT4_ERRORS_CONTINUE 1
#define EXT4_ERRORS_RO 2
#define EXT4_ERRORS_PANIC 3
#define EXT4_LINUX_ID 0
#define EXT4_GNU_HURD_ID 1
#define EXT4_MASIX_ID 2
#define EXT4_FREEBSD_ID 3
#define EXT4_LITES_ID 4
#define EXT4_GOOD_OLD_REV 0
#define EXT4_DYNAMIC_REV 1
#define EXT4_CHECKSUM_CRC32C 0x1
#define EXT4_FEATURE_COMPAT_DIR_PREALLOC 0x01
#define EXT4_FEATURE_COMPAT_IMAGIC_INODES 0x02
#define EXT3_FEATURE_COMPAT_HAS_JOURNAL 0x04
#define EXT4_FEATURE_COMPAT_EXT_ATTR 0x08
#define EXT4_FEATURE_COMPAT_RESIZE_INO 0x10
#define EXT4_FEATURE_COMPAT_DIR_INDEX 0x20
#define EXT4_FEATURE_INCOMPAT_COMPRESSION 0x00001
#define EXT4_FEATURE_INCOMPAT_FILETYPE 0x00002
#define EXT4_FEATURE_INCOMPAT_RECOVER 0x00004
#define EXT4_FEATURE_INCOMPAT_JOURNAL_DEV 0x00008
#define EXT4_FEATURE_INCOMPAT_META_BG 0x00010
#define EXT4_FEATURE_INCOMPAT_EXTENTS 0x00040
#define EXT4_FEATURE_INCOMPAT_64BIT 0x00080
#define EXT4_FEATURE_INCOMPAT_MMP 0x00100
#define EXT4_FEATURE_INCOMPAT_FLEX_BG 0x00200
#define EXT4_FEATURE_INCOMPAT_EA_INODE 0x00400
// It's not clear whether or not this feature (below) is used right now
#define EXT4_FEATURE_INCOMPAT_DIRDATA 0x01000
#define EXT4_FEATURE_INCOMPAT_CSUM_SEED 0x02000
#define EXT4_FEATURE_INCOMPAT_LARGEDIR 0x04000
#define EXT4_FEATURE_INCOMPAT_INLINE_DATA 0x08000
#define EXT4_FEATURE_INCOMPAT_ENCRYPT 0x10000
#define EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER 0x0001
#define EXT4_FEATURE_RO_COMPAT_LARGE_FILE 0x0002
#define EXT4_FEATURE_RO_COMPAT_BTREE_DIR 0x0004// Unused
#define EXT4_FEATURE_RO_COMPAT_HUGE_FILE 0x0008
#define EXT4_FEATURE_RO_COMPAT_GDT_CSUM 0x0010
#define EXT4_FEATURE_RO_COMPAT_DIR_NLINK 0x0020
#define EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE 0x0040
#define EXT4_FEATURE_RO_COMPAT_HAS_SNAPSHOT 0x0080// Not implemented in ext4
#define EXT4_FEATURE_RO_COMPAT_QUOTA 0x0100
#define EXT4_FEATURE_RO_COMPAT_BIGALLOC 0x0200
#define EXT4_FEATURE_RO_COMPAT_METADATA_CSUM 0x0400
#define EXT4_FEATURE_RO_COMPAT_REPLICA 0x0800// Not used
// We explicitly don't recognise this, so we get read only.
#define EXT4_FEATURE_RO_COMPAT_READONLY 0x1000
#define EXT4_FEATURE_RO_COMPAT_PROJECT 0x2000
/* Important notes about the features
* Absolutely needed features:
* 1) Every incompat, because we might want to mount root filesystems
* 2) Relevant RO_COMPATs(I'm not sure of what to do wrt quota, project)
**/
#define EXT4_INO_TYPE_FIFO 0x1000
#define EXT4_INO_TYPE_CHARDEV 0x2000
#define EXT4_INO_TYPE_DIR 0x4000
#define EXT4_INO_TYPE_BLOCKDEV 0x6000
#define EXT4_INO_TYPE_REGFILE 0x8000
#define EXT4_INO_TYPE_SYMLINK 0xA000
#define EXT4_INO_TYPE_UNIX_SOCK 0xC000
/* Inode flags */
#define EXT4_SECRM_FL 0x00000001
#define EXT4_UNRM_FL 0x00000002
#define EXT4_COMPR_FL 0x00000004
#define EXT4_SYNC_FL 0x00000008
#define EXT4_IMMUTABLE_FL 0x00000010
#define EXT4_APPEND_FL 0x00000020
#define EXT4_NODUMP_FL 0x00000040
#define EXT4_NOATIME_FL 0x00000080
#define EXT4_DIRTY_FL 0x00000100
#define EXT4_COMPRBLK_FL 0x00000200
#define EXT4_NOCOMPR_FL 0x00000400
#define EXT4_ENCRYPT_FL 0x00000800
#define EXT4_BTREE_FL 0x00001000
#define EXT4_INDEX_FL 0x00002000
#define EXT4_JOURNAL_DATA_FL 0x00004000
#define EXT4_NOTAIL_FL 0x00008000
#define EXT4_DIRSYNC_FL 0x00010000
#define EXT4_TOPDIR_FL 0x00020000
#define EXT4_HUGE_FILE_FL 0x00040000
#define EXT4_EXTENTS_FL 0x00080000
#define EXT4_VERITY_FL 0x00100000
#define EXT4_EA_INODE_FL 0x00200000
#define EXT4_RESERVED_FL 0x80000000
/* File type flags that are stored in the directory entries */
#define EXT4_FT_UNKNOWN 0
#define EXT4_FT_REG_FILE 1
#define EXT4_FT_DIR 2
#define EXT4_FT_CHRDEV 3
#define EXT4_FT_BLKDEV 4
#define EXT4_FT_FIFO 5
#define EXT4_FT_SOCK 6
#define EXT4_FT_SYMLINK 7
typedef struct {
UINT32 s_inodes_count;
UINT32 s_blocks_count;
UINT32 s_r_blocks_count;
UINT32 s_free_blocks_count;
UINT32 s_free_inodes_count;
UINT32 s_first_data_block;
UINT32 s_log_block_size;
UINT32 s_log_frag_size;
UINT32 s_blocks_per_group;
UINT32 s_frags_per_group;
UINT32 s_inodes_per_group;
UINT32 s_mtime;
UINT32 s_wtime;
UINT16 s_mnt_count;
UINT16 s_max_mnt_count;
UINT16 s_magic;
UINT16 s_state;
UINT16 s_errors;
UINT16 s_minor_rev_level;
UINT32 s_lastcheck;
UINT32 s_check_interval;
UINT32 s_creator_os;
UINT32 s_rev_level;
UINT16 s_def_resuid;
UINT16 s_def_resgid;
/* Every field after this comment is revision >= 1 */
UINT32 s_first_ino;
UINT16 s_inode_size;
UINT16 s_block_group_nr;
UINT32 s_feature_compat;
UINT32 s_feature_incompat;
UINT32 s_feature_ro_compat;
UINT8 s_uuid[16];
UINT8 s_volume_name[16];
UINT8 s_last_mounted[64];
UINT32 s_algo_bitmap;
UINT8 s_prealloc_blocks;
UINT8 s_prealloc_dir_blocks;
UINT16 unused;
UINT8 s_journal_uuid[16];
UINT32 s_journal_inum;
UINT32 s_journal_dev;
UINT32 s_last_orphan;
UINT32 s_hash_seed[4];
UINT8 s_def_hash_version;
UINT8 s_jnl_backup_type;
UINT16 s_desc_size;
UINT32 s_default_mount_options;
UINT32 s_first_meta_bg;
UINT32 s_mkfs_time;
UINT32 s_jnl_blocks[17];
UINT32 s_blocks_count_hi;
UINT32 s_r_blocks_count_hi;
UINT32 s_free_blocks_count_hi;
UINT16 s_min_extra_isize;
UINT16 s_want_extra_isize;
UINT32 s_flags;
UINT16 s_raid_stride;
UINT16 s_mmp_interval;
UINT64 s_mmp_block;
UINT32 s_raid_stride_width;
UINT8 s_log_groups_per_flex;
UINT8 s_checksum_type; // Only valid value is 1 - CRC32C
UINT16 s_reserved_pad;
UINT64 s_kbytes_written;
// Snapshot stuff isn't used in Linux and isn't implemented here
UINT32 s_snapshot_inum;
UINT32 s_snapshot_id;
UINT64 s_snapshot_r_blocks_count;
UINT32 s_snapshot_list;
UINT32 s_error_count;
UINT32 s_first_error_time;
UINT32 s_first_error_ino;
UINT64 s_first_error_block;
UINT8 s_first_error_func[32];
UINT32 s_first_error_line;
UINT32 s_last_error_time;
UINT32 s_last_error_ino;
UINT32 s_last_error_line;
UINT64 s_last_error_block;
UINT8 s_last_error_func[32];
UINT8 s_mount_opts[64];
UINT32 s_usr_quota_inum;
UINT32 s_grp_quota_inum;
UINT32 s_overhead_blocks;
UINT32 s_backup_bgs[2]; // sparse_super2
UINT8 s_encrypt_algos[4];
UINT8 s_encrypt_pw_salt[16];
UINT32 s_lpf_ino;
UINT32 s_prj_quota_inum;
UINT32 s_checksum_seed;
UINT32 s_reserved[98];
UINT32 s_checksum;
} EXT4_SUPERBLOCK;
STATIC_ASSERT (
sizeof (EXT4_SUPERBLOCK) == 1024,
"ext4 superblock struct has incorrect size"
);
typedef struct {
UINT32 bg_block_bitmap_lo;
UINT32 bg_inode_bitmap_lo;
UINT32 bg_inode_table_lo;
UINT16 bg_free_blocks_count_lo;
UINT16 bg_free_inodes_count_lo;
UINT16 bg_used_dirs_count_lo;
UINT16 bg_flags;
UINT32 bg_exclude_bitmap_lo;
UINT16 bg_block_bitmap_csum_lo;
UINT16 bg_inode_bitmap_csum_lo;
UINT16 bg_itable_unused_lo;
UINT16 bg_checksum;
UINT32 bg_block_bitmap_hi;
UINT32 bg_inode_bitmap_hi;
UINT32 bg_inode_table_hi;
UINT16 bg_free_blocks_count_hi;
UINT16 bg_free_inodes_count_hi;
UINT16 bg_used_dirs_count_hi;
UINT16 bg_itable_unused_hi;
UINT32 bg_exclude_bitmap_hi;
UINT16 bg_block_bitmap_csum_hi;
UINT16 bg_inode_bitmap_csum_hi;
UINT32 bg_reserved;
} EXT4_BLOCK_GROUP_DESC;
#define EXT4_OLD_BLOCK_DESC_SIZE 32
#define EXT4_64BIT_BLOCK_DESC_SIZE 64
STATIC_ASSERT (
sizeof (EXT4_BLOCK_GROUP_DESC) == EXT4_64BIT_BLOCK_DESC_SIZE,
"ext4 block group descriptor struct has incorrect size"
);
#define EXT4_DBLOCKS 12
#define EXT4_IND_BLOCK 12
#define EXT4_DIND_BLOCK 13
#define EXT4_TIND_BLOCK 14
#define EXT4_NR_BLOCKS 15
#define EXT4_FAST_SYMLINK_MAX_SIZE EXT4_NR_BLOCKS * sizeof(UINT32)
#define EXT4_GOOD_OLD_INODE_SIZE 128U
typedef struct _Ext4_I_OSD2_Linux {
UINT16 l_i_blocks_high;
UINT16 l_i_file_acl_high;
UINT16 l_i_uid_high;
UINT16 l_i_gid_high;
UINT16 l_i_checksum_lo;
UINT16 l_i_reserved;
} EXT4_OSD2_LINUX;
typedef struct _Ext4_I_OSD2_Hurd {
UINT16 h_i_reserved1;
UINT16 h_i_mode_high;
UINT16 h_i_uid_high;
UINT16 h_i_gid_high;
UINT32 h_i_author;
} EXT4_OSD2_HURD;
typedef union {
// Note: Toolchain-specific defines (such as "linux") stops us from using
// simpler names down here.
EXT4_OSD2_LINUX data_linux;
EXT4_OSD2_HURD data_hurd;
} EXT4_OSD2;
typedef struct _Ext4Inode {
UINT16 i_mode;
UINT16 i_uid;
UINT32 i_size_lo;
UINT32 i_atime;
UINT32 i_ctime;
UINT32 i_mtime;
UINT32 i_dtime;
UINT16 i_gid;
UINT16 i_links;
UINT32 i_blocks;
UINT32 i_flags;
UINT32 i_os_spec;
UINT32 i_data[EXT4_NR_BLOCKS];
UINT32 i_generation;
UINT32 i_file_acl;
UINT32 i_size_hi;
UINT32 i_faddr;
EXT4_OSD2 i_osd2;
UINT16 i_extra_isize;
UINT16 i_checksum_hi;
UINT32 i_ctime_extra;
UINT32 i_mtime_extra;
UINT32 i_atime_extra;
UINT32 i_crtime;
UINT32 i_crtime_extra;
UINT32 i_version_hi;
UINT32 i_projid;
} EXT4_INODE;
#define EXT4_NAME_MAX 255
typedef struct {
// offset 0x0: inode number (if 0, unused entry, should skip.)
UINT32 inode;
// offset 0x4: Directory entry's length.
// Note: rec_len >= name_len + EXT4_MIN_DIR_ENTRY_LEN and rec_len % 4 == 0.
UINT16 rec_len;
// offset 0x6: Directory entry's name's length
UINT8 name_len;
// offset 0x7: Directory entry's file type indicator
UINT8 file_type;
// offset 0x8: name[name_len]: Variable length character array; not null-terminated.
CHAR8 name[EXT4_NAME_MAX];
// Further notes on names:
// 1) We use EXT4_NAME_MAX here instead of flexible arrays for ease of use around the driver.
//
// 2) ext4 directories are defined, as the documentation puts it, as:
// "a directory is more or less a flat file that maps an arbitrary byte string
// (usually ASCII) to an inode number on the filesystem". So, they are not
// necessarily encoded with ASCII, UTF-8, or any of the sort. We must treat it
// as a bag of bytes. When interacting with EFI interfaces themselves (which expect UCS-2)
// we skip any directory entry that is not valid UTF-8.
} EXT4_DIR_ENTRY;
#define EXT4_MIN_DIR_ENTRY_LEN 8
// This on-disk structure is present at the bottom of the extent tree
typedef struct {
// First logical block
UINT32 ee_block;
// Length of the extent, in blocks
UINT16 ee_len;
// The physical (filesystem-relative) block is split between the high 16 bits
// and the low 32 bits - this forms a 48-bit block number
UINT16 ee_start_hi;
UINT32 ee_start_lo;
} EXT4_EXTENT;
// This on-disk structure is present at all levels except the bottom
typedef struct {
// This index covers logical blocks from 'ei_block'
UINT32 ei_block;
// Block of the next level of the extent tree, similarly split in a high and
// low portion.
UINT32 ei_leaf_lo;
UINT16 ei_leaf_hi;
UINT16 ei_unused;
} EXT4_EXTENT_INDEX;
typedef struct {
// Needs to be EXT4_EXTENT_HEADER_MAGIC
UINT16 eh_magic;
// Number of entries
UINT16 eh_entries;
// Maximum number of entries that could follow this header
UINT16 eh_max;
// Depth of this node in the tree - the tree can be at most 5 levels deep
UINT16 eh_depth;
// Unused by standard ext4
UINT32 eh_generation;
} EXT4_EXTENT_HEADER;
#define EXT4_EXTENT_HEADER_MAGIC 0xF30A
// Specified by ext4 docs and backed by a bunch of math
#define EXT4_EXTENT_TREE_MAX_DEPTH 5
typedef struct {
// CRC32C of UUID + inode number + igeneration + extent block
UINT32 eb_checksum;
} EXT4_EXTENT_TAIL;
/**
* EXT4 has this feature called uninitialized extents:
* An extent has a maximum of 32768 blocks (2^15 or 1 << 15).
* When we find an extent with > 32768 blocks, this extent is called
* uninitialized. Long story short, it's an extent that behaves as a file hole
* but has blocks already allocated.
*/
#define EXT4_EXTENT_MAX_INITIALIZED (1 << 15)
typedef UINT64 EXT4_BLOCK_NR;
typedef UINT32 EXT2_BLOCK_NR;
typedef UINT32 EXT4_INO_NR;
/* Special inode numbers */
#define EXT4_ROOT_INODE_NR 2
#define EXT4_USR_QUOTA_INODE_NR 3
#define EXT4_GRP_QUOTA_INODE_NR 4
#define EXT4_BOOT_LOADER_INODE_NR 5
#define EXT4_UNDEL_DIR_INODE_NR 6
#define EXT4_RESIZE_INODE_NR 7
#define EXT4_JOURNAL_INODE_NR 8
/* First non-reserved inode for old ext4 filesystems */
#define EXT4_GOOD_OLD_FIRST_INODE_NR 11
#define EXT4_BLOCK_FILE_HOLE 0
#endif
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