408 lines
13 KiB
C
408 lines
13 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Copyright 2018 Google LLC
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*/
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/*
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* Overview
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* --------
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* The backbone of the incremental-fs ondisk format is an append only linked
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* list of metadata blocks. Each metadata block contains an offset of the next
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* one. These blocks describe files and directories on the
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* file system. They also represent actions of adding and removing file names
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* (hard links).
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*
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* Every time incremental-fs instance is mounted, it reads through this list
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* to recreate filesystem's state in memory. An offset of the first record in
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* the metadata list is stored in the superblock at the beginning of the backing
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* file.
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*
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* Most of the backing file is taken by data areas and blockmaps.
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* Since data blocks can be compressed and have different sizes,
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* single per-file data area can't be pre-allocated. That's why blockmaps are
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* needed in order to find a location and size of each data block in
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* the backing file. Each time a file is created, a corresponding block map is
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* allocated to store future offsets of data blocks.
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*
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* Whenever a data block is given by data loader to incremental-fs:
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* - A data area with the given block is appended to the end of
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* the backing file.
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* - A record in the blockmap for the given block index is updated to reflect
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* its location, size, and compression algorithm.
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* Metadata records
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* ----------------
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* incfs_blockmap - metadata record that specifies size and location
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* of a blockmap area for a given file. This area
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* contains an array of incfs_blockmap_entry-s.
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* incfs_file_signature - metadata record that specifies where file signature
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* and its hash tree can be found in the backing file.
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*
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* incfs_file_attr - metadata record that specifies where additional file
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* attributes blob can be found.
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*
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* Metadata header
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* ---------------
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* incfs_md_header - header of a metadata record. It's always a part
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* of other structures and served purpose of metadata
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* bookkeeping.
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*
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* +-----------------------------------------------+ ^
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* | incfs_md_header | |
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* | 1. type of body(BLOCKMAP, FILE_ATTR..) | |
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* | 2. size of the whole record header + body | |
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* | 3. CRC the whole record header + body | |
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* | 4. offset of the previous md record |]------+
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* | 5. offset of the next md record (md link) |]---+
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* +-----------------------------------------------+ |
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* | Metadata record body with useful data | |
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* +-----------------------------------------------+ |
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* +--->
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*
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* Other ondisk structures
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* -----------------------
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* incfs_super_block - backing file header
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* incfs_blockmap_entry - a record in a blockmap area that describes size
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* and location of a data block.
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* Data blocks dont have any particular structure, they are written to the
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* backing file in a raw form as they come from a data loader.
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*
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* Backing file layout
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* -------------------
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*
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*
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* +-------------------------------------------+
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* | incfs_file_header |]---+
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* +-------------------------------------------+ |
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* | metadata |<---+
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* | incfs_file_signature |]---+
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* +-------------------------------------------+ |
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* ......................... |
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* +-------------------------------------------+ | metadata
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* +------->| blockmap area | | list links
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* | | [incfs_blockmap_entry] | |
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* | | [incfs_blockmap_entry] | |
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* | | [incfs_blockmap_entry] | |
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* | +--[| [incfs_blockmap_entry] | |
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* | | | [incfs_blockmap_entry] | |
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* | | | [incfs_blockmap_entry] | |
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* | | +-------------------------------------------+ |
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* | | ......................... |
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* | | +-------------------------------------------+ |
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* | | | metadata |<---+
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* +----|--[| incfs_blockmap |]---+
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* | +-------------------------------------------+ |
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* | ......................... |
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* | +-------------------------------------------+ |
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* +-->| data block | |
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* +-------------------------------------------+ |
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* ......................... |
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* +-------------------------------------------+ |
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* | metadata |<---+
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* | incfs_file_attr |
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* +-------------------------------------------+
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*/
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#ifndef _INCFS_FORMAT_H
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#define _INCFS_FORMAT_H
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <uapi/linux/incrementalfs.h>
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#include "internal.h"
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#define INCFS_MAX_NAME_LEN 255
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#define INCFS_FORMAT_V1 1
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#define INCFS_FORMAT_CURRENT_VER INCFS_FORMAT_V1
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enum incfs_metadata_type {
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INCFS_MD_NONE = 0,
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INCFS_MD_BLOCK_MAP = 1,
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INCFS_MD_FILE_ATTR = 2,
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INCFS_MD_SIGNATURE = 3,
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INCFS_MD_STATUS = 4,
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INCFS_MD_VERITY_SIGNATURE = 5,
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};
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enum incfs_file_header_flags {
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INCFS_FILE_MAPPED = 1 << 1,
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};
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/* Header included at the beginning of all metadata records on the disk. */
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struct incfs_md_header {
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__u8 h_md_entry_type;
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/*
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* Size of the metadata record.
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* (e.g. inode, dir entry etc) not just this struct.
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*/
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__le16 h_record_size;
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/*
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* Was: CRC32 of the metadata record.
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* (e.g. inode, dir entry etc) not just this struct.
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*/
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__le32 h_unused1;
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/* Offset of the next metadata entry if any */
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__le64 h_next_md_offset;
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/* Was: Offset of the previous metadata entry if any */
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__le64 h_unused2;
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} __packed;
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/* Backing file header */
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struct incfs_file_header {
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/* Magic number: INCFS_MAGIC_NUMBER */
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__le64 fh_magic;
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/* Format version: INCFS_FORMAT_CURRENT_VER */
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__le64 fh_version;
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/* sizeof(incfs_file_header) */
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__le16 fh_header_size;
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/* INCFS_DATA_FILE_BLOCK_SIZE */
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__le16 fh_data_block_size;
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/* File flags, from incfs_file_header_flags */
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__le32 fh_flags;
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union {
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/* Standard incfs file */
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struct {
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/* Offset of the first metadata record */
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__le64 fh_first_md_offset;
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/* Full size of the file's content */
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__le64 fh_file_size;
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/* File uuid */
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incfs_uuid_t fh_uuid;
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};
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/* Mapped file - INCFS_FILE_MAPPED set in fh_flags */
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struct {
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/* Offset in original file */
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__le64 fh_original_offset;
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/* Full size of the file's content */
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__le64 fh_mapped_file_size;
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/* Original file's uuid */
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incfs_uuid_t fh_original_uuid;
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};
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};
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} __packed;
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enum incfs_block_map_entry_flags {
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INCFS_BLOCK_COMPRESSED_LZ4 = 1,
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INCFS_BLOCK_COMPRESSED_ZSTD = 2,
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/* Reserve 3 bits for compression alg */
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INCFS_BLOCK_COMPRESSED_MASK = 7,
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};
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/* Block map entry pointing to an actual location of the data block. */
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struct incfs_blockmap_entry {
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/* Offset of the actual data block. Lower 32 bits */
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__le32 me_data_offset_lo;
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/* Offset of the actual data block. Higher 16 bits */
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__le16 me_data_offset_hi;
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/* How many bytes the data actually occupies in the backing file */
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__le16 me_data_size;
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/* Block flags from incfs_block_map_entry_flags */
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__le16 me_flags;
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} __packed;
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/* Metadata record for locations of file blocks. Type = INCFS_MD_BLOCK_MAP */
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struct incfs_blockmap {
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struct incfs_md_header m_header;
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/* Base offset of the array of incfs_blockmap_entry */
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__le64 m_base_offset;
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/* Size of the map entry array in blocks */
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__le32 m_block_count;
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} __packed;
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/*
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* Metadata record for file signature. Type = INCFS_MD_SIGNATURE
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*
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* The signature stored here is the APK V4 signature data blob. See the
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* definition of incfs_new_file_args::signature_info for an explanation of this
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* blob. Specifically, it contains the root hash, but it does *not* contain
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* anything that the kernel treats as a signature.
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*
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* When FS_IOC_ENABLE_VERITY is called on a file without this record, an APK V4
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* signature blob and a hash tree are added to the file, and then this metadata
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* record is created to record their locations.
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*/
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struct incfs_file_signature {
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struct incfs_md_header sg_header;
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__le32 sg_sig_size; /* The size of the signature. */
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__le64 sg_sig_offset; /* Signature's offset in the backing file */
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__le32 sg_hash_tree_size; /* The size of the hash tree. */
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__le64 sg_hash_tree_offset; /* Hash tree offset in the backing file */
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} __packed;
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/* In memory version of above */
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struct incfs_df_signature {
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u32 sig_size;
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u64 sig_offset;
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u32 hash_size;
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u64 hash_offset;
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};
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struct incfs_status {
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struct incfs_md_header is_header;
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__le32 is_data_blocks_written; /* Number of data blocks written */
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__le32 is_hash_blocks_written; /* Number of hash blocks written */
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__le32 is_dummy[6]; /* Spare fields */
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} __packed;
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/*
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* Metadata record for verity signature. Type = INCFS_MD_VERITY_SIGNATURE
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*
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* This record will only exist for verity-enabled files with signatures. Verity
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* enabled files without signatures do not have this record. This signature is
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* checked by fs-verity identically to any other fs-verity signature.
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*/
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struct incfs_file_verity_signature {
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struct incfs_md_header vs_header;
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/* The size of the signature */
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__le32 vs_size;
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/* Signature's offset in the backing file */
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__le64 vs_offset;
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} __packed;
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/* In memory version of above */
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struct incfs_df_verity_signature {
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u32 size;
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u64 offset;
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};
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/* State of the backing file. */
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struct backing_file_context {
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/* Protects writes to bc_file */
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struct mutex bc_mutex;
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/* File object to read data from */
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struct file *bc_file;
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/*
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* Offset of the last known metadata record in the backing file.
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* 0 means there are no metadata records.
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*/
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loff_t bc_last_md_record_offset;
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/*
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* Credentials to set before reads/writes
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* Note that this is a pointer to the mount_info mi_owner field so
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* there is no need to get/put the creds
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*/
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const struct cred *bc_cred;
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};
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struct metadata_handler {
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loff_t md_record_offset;
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loff_t md_prev_record_offset;
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void *context;
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union {
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struct incfs_md_header md_header;
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struct incfs_blockmap blockmap;
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struct incfs_file_signature signature;
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struct incfs_status status;
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struct incfs_file_verity_signature verity_signature;
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} md_buffer;
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int (*handle_blockmap)(struct incfs_blockmap *bm,
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struct metadata_handler *handler);
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int (*handle_signature)(struct incfs_file_signature *sig,
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struct metadata_handler *handler);
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int (*handle_status)(struct incfs_status *sig,
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struct metadata_handler *handler);
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int (*handle_verity_signature)(struct incfs_file_verity_signature *s,
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struct metadata_handler *handler);
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};
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#define INCFS_MAX_METADATA_RECORD_SIZE \
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FIELD_SIZEOF(struct metadata_handler, md_buffer)
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/* Backing file context management */
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struct mount_info;
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struct backing_file_context *incfs_alloc_bfc(struct mount_info *mi,
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struct file *backing_file);
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void incfs_free_bfc(struct backing_file_context *bfc);
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/* Writing stuff */
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int incfs_write_blockmap_to_backing_file(struct backing_file_context *bfc,
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u32 block_count);
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int incfs_write_fh_to_backing_file(struct backing_file_context *bfc,
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incfs_uuid_t *uuid, u64 file_size);
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int incfs_write_mapping_fh_to_backing_file(struct backing_file_context *bfc,
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incfs_uuid_t *uuid, u64 file_size, u64 offset);
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int incfs_write_data_block_to_backing_file(struct backing_file_context *bfc,
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struct mem_range block,
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int block_index, loff_t bm_base_off,
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u16 flags);
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int incfs_write_hash_block_to_backing_file(struct backing_file_context *bfc,
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struct mem_range block,
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int block_index,
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loff_t hash_area_off,
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loff_t bm_base_off,
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loff_t file_size);
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int incfs_write_signature_to_backing_file(struct backing_file_context *bfc,
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struct mem_range sig, u32 tree_size,
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loff_t *tree_offset, loff_t *sig_offset);
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int incfs_write_status_to_backing_file(struct backing_file_context *bfc,
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loff_t status_offset,
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u32 data_blocks_written,
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u32 hash_blocks_written);
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int incfs_write_verity_signature_to_backing_file(
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struct backing_file_context *bfc, struct mem_range signature,
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loff_t *offset);
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/* Reading stuff */
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int incfs_read_file_header(struct backing_file_context *bfc,
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loff_t *first_md_off, incfs_uuid_t *uuid,
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u64 *file_size, u32 *flags);
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int incfs_read_blockmap_entry(struct backing_file_context *bfc, int block_index,
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loff_t bm_base_off,
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struct incfs_blockmap_entry *bm_entry);
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int incfs_read_blockmap_entries(struct backing_file_context *bfc,
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struct incfs_blockmap_entry *entries,
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int start_index, int blocks_number,
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loff_t bm_base_off);
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int incfs_read_next_metadata_record(struct backing_file_context *bfc,
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struct metadata_handler *handler);
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ssize_t incfs_kread(struct backing_file_context *bfc, void *buf, size_t size,
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loff_t pos);
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ssize_t incfs_kwrite(struct backing_file_context *bfc, const void *buf,
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size_t size, loff_t pos);
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#endif /* _INCFS_FORMAT_H */
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