From cf7e7d4c30097f02f58d43979abb0915a992b06a Mon Sep 17 00:00:00 2001
From: pigeonmoelleux <pigeonmoelleux@crans.org>
Date: Fri, 19 May 2023 22:59:49 +0200
Subject: [PATCH] feat(fs): ext2 superblock
---
src/fs/ext2/mod.rs | 4 +
src/fs/ext2/superblock.rs | 274 ++++++++++++++++++++++++++++++++++++++
src/fs/mod.rs | 2 +
src/fs/vfs.rs | 3 +
4 files changed, 283 insertions(+)
create mode 100644 src/fs/ext2/mod.rs
create mode 100644 src/fs/ext2/superblock.rs
create mode 100644 src/fs/vfs.rs
diff --git a/src/fs/ext2/mod.rs b/src/fs/ext2/mod.rs
new file mode 100644
index 0000000..2dcff89
--- /dev/null
+++ b/src/fs/ext2/mod.rs
@@ -0,0 +1,4 @@
+//! Implementation of the Second Extended Filesystem (ext2fs) filesystem
+
+#[allow(clippy::same_name_method)]
+mod superblock;
diff --git a/src/fs/ext2/superblock.rs b/src/fs/ext2/superblock.rs
new file mode 100644
index 0000000..9ebe521
--- /dev/null
+++ b/src/fs/ext2/superblock.rs
@@ -0,0 +1,274 @@
+//! Interface with the superblock
+//!
+//! See the [OSdev wiki](https://wiki.osdev.org/Ext2#Superblock) for more informations
+
+use bitflags::bitflags;
+use log::error;
+
+/// Superblock of the ext2 filesystem
+///
+/// This implementation contains also the extended fields described [here](https://wiki.osdev.org/Ext2#Extended_Superblock_Fields)
+#[repr(packed)]
+#[derive(Debug)]
+pub struct Superblock {
+ /// Total number of inodes in file system
+ pub total_inodes: u32,
+
+ /// Total number of blocks in file system
+ pub total_blocks: u32,
+
+ /// Number of blocks reserved for superuser (see offset 80)
+ pub number_blocks_superuser_reserved: u32,
+
+ /// Total number of unallocated blocks
+ pub total_unallocated_blocks: u32,
+
+ /// Total number of unallocated inodes
+ pub total_unallocated_inodes: u32,
+
+ /// Block number of the block containing the superblock (also the starting block number, NOT always zero.)
+ pub superblock_block_number: u32,
+
+ /// log2 (block size) - 10. (In other words, the number to shift 1,024 to the left by to obtain the block size)
+ pub shifted_block_size: u32,
+
+ /// log2 (fragment size) - 10. (In other words, the number to shift 1,024 to the left by to obtain the fragment size)
+ pub shifted_fragment_size: u32,
+
+ /// Number of blocks in each block group
+ pub blocks_per_group: u32,
+
+ /// Number of fragments in each block group
+ pub fragments_per_group: u32,
+
+ /// Number of inodes in each block group
+ pub inodes_per_group: u32,
+
+ /// Last mount time (in POSIX time)
+ pub last_mount_time: u32,
+
+ /// Last written time (in POSIX time)
+ pub last_written_time: u32,
+
+ /// Number of times the volume has been mounted since its last consistency check (fsck)
+ pub nb_volumes_mounted_since_fsck: u16,
+
+ /// Number of mounts allowed before a consistency check (fsck) must be done
+ pub nb_mounts_before_fsck: u16,
+
+ /// Ext2 signature (0xef53), used to help confirm the presence of Ext2 on a volume
+ pub ext2_signature: u16,
+
+ /// File system state
+ pub file_system_state: u16,
+
+ /// What to do when an error is detected
+ pub error_handling_method: u16,
+
+ /// Minor portion of version (combine with Major portion below to construct full version field)
+ pub version_minor: u16,
+
+ /// POSIX time of last consistency check (fsck)
+ pub time_last_fsck: u32,
+
+ /// Interval (in POSIX time) between forced consistency checks (fsck)
+ pub interval_forced_fsck: u32,
+
+ /// Operating system ID from which the filesystem on this volume was created
+ pub os_id: u32,
+
+ /// Major portion of version (combine with Minor portion above to construct full version field)
+ pub version_major: u32,
+
+ /// User ID that can use reserved blocks
+ pub reserved_blocks_user_id: u16,
+
+ /// Group ID that can use reserved blocks
+ pub reserved_blocks_group_id: u16,
+
+ /// First non-reserved inode in file system. (In versions < 1.0, this is fixed as 11)
+ pub first_non_reserved_inode: u32,
+
+ /// Size of each inode structure in bytes. (In versions < 1.0, this is fixed as 128)
+ pub inode_byte_size: u16,
+
+ /// Block group that this superblock is part of (if backup copy)
+ pub superblock_block_number_backup_copy: u16,
+
+ /// Optional features present (features that are not required to read or write, but usually result in a performance increase)
+ pub optional_features: u32,
+
+ /// Required features present (features that are required to be supported to read or write)
+ pub required_features: u32,
+
+ /// Features that if not supported, the volume must be mounted read-only
+ pub forced_read_only_features: u32,
+
+ /// File system ID (what is output by blkid)
+ pub file_system_id: u128,
+
+ /// Volume name (C-style string: characters terminated by a 0 byte)
+ pub volume_name: [u8; 16],
+
+ /// Path volume was last mounted to (C-style string: characters terminated by a 0 byte)
+ pub path_last_mount: [u8; 64],
+
+ /// Compression algorithms used (see Required features above)
+ pub compression_algorithms: u32,
+
+ /// Number of blocks to preallocate for files
+ pub preallocated_blocks_per_file: u8,
+
+ /// Number of blocks to preallocate for directories
+ pub preallocated_blocks_per_dir: u8,
+
+ /// (Unused)
+ pub _unused: u16,
+
+ /// Journal ID (same style as the File system ID above)
+ pub journal_id: u128,
+
+ /// Journal inode
+ pub journal_inode: u32,
+
+ /// Journal device
+ pub journal_device: u32,
+
+ /// Head of orphan inode list
+ pub head_orphan_node_list: u32,
+}
+
+/// File System States
+///
+/// See the [OSdev wiki](https://wiki.osdev.org/Ext2#File_System_States) for more informations
+#[repr(u16)]
+#[derive(Debug)]
+pub enum State {
+ /// File system is clean
+ Clean = 0x0001,
+
+ /// File system has errors
+ Errors = 0x0002,
+}
+
+impl TryFrom<u16> for State {
+ type Error = anyhow::Error;
+
+ fn try_from(value: u16) -> Result<Self, Self::Error> {
+ match value {
+ 0x0001 => Ok(Self::Clean),
+ 0x0002 => Ok(Self::Errors),
+ _ => {
+ error!("ext2 superblock: tried to convert {:x} into a state (which can only be 1 or 2)", value);
+ Err(anyhow::Error::msg("ext2 superblock: tried to convert a value different than 1 or 2 into a state"))
+ },
+ }
+ }
+}
+
+impl From<State> for u16 {
+ fn from(value: State) -> Self {
+ value as Self
+ }
+}
+
+/// Error Handling Methods
+///
+/// See the [OSdev wiki](https://wiki.osdev.org/Ext2#Error_Handling_Methods) for more informations
+#[repr(u16)]
+#[derive(Debug)]
+pub enum ErrorsHandling {
+ /// Ignore the error (continue on)
+ Ignore = 0x0001,
+
+ /// Remount file system as read-only
+ Remount = 0x0002,
+
+ /// Kernel panic
+ Panic = 0x03,
+}
+
+impl TryFrom<u16> for ErrorsHandling {
+ type Error = anyhow::Error;
+
+ fn try_from(value: u16) -> Result<Self, Self::Error> {
+ match value {
+ 0x0001 => Ok(Self::Ignore),
+ 0x0002 => Ok(Self::Remount),
+ 0x0003 => Ok(Self::Panic),
+ _ => {
+ error!(
+ "ext2 superblock: tried to convert {:x} into an error handling method (which can only between 1 and 3)",
+ value
+ );
+ Err(anyhow::Error::msg(
+ "ext2 superblock: tried to convert a value different than 1, 2 or 3 into an error handling method",
+ ))
+ },
+ }
+ }
+}
+
+impl From<ErrorsHandling> for u16 {
+ fn from(value: ErrorsHandling) -> Self {
+ value as Self
+ }
+}
+
+bitflags! {
+ /// These are optional features for an implementation to support, but offer performance or reliability gains to
+ /// implementations that do support them.
+ pub struct OptionalFeatures: u16 {
+ /// Preallocate some number of (contiguous?) blocks (see byte 205 in the superblock) to a directory when creating
+ /// a new one (to reduce fragmentation?)
+ const PREALLOCATE_BLOCS = 0x0001;
+
+ /// AFS server inodes exist
+ const AFS = 0x0002;
+
+ /// File system has a journal (Ext3)
+ const JOURNAL_DEVICE = 0x0004;
+
+ /// Inodes have extended attributes
+ const INODES_EXTENDED_ATTRIBUTES = 0x0008;
+
+ /// File system can resize itself for larger partitions
+ const RESIZE_PARTITIONS = 0x0010;
+
+ /// Directories use hash index
+ const HASH_INDEX = 0x0020;
+ }
+}
+
+bitflags! {
+ /// These features if present on a file system are required to be supported by an implementation in order to correctly
+ /// read from or write to the file system
+ pub struct RequiredFeatures: u16 {
+ /// Compression is used
+ const COMPRESSION = 0x0001;
+
+ /// Directory entries contain a type field
+ const TYPE_FIELD = 0x0002;
+
+ /// File system needs to replay its journal
+ const JOURNAL_REPLAY = 0x0004;
+
+ /// File system uses a journal device
+ const JOURNAL_DEVICE = 0x0008;
+ }
+}
+
+bitflags! {
+ /// These features, if present on a file system, are required in order for an implementation to write to the file system,
+ /// but are not required to read from the file system.
+ pub struct ReadOnlyFeatures: u16 {
+ /// Sparse superblocks and group descriptor tables
+ const SPARSE_SUPERBLOCKS = 0x0001;
+
+ /// File system uses a 64-bit file size
+ const SIZE_64_BITS = 0x0002;
+
+ /// Directory contents are stored in the form of a Binary Tree
+ const BINARY_TREE = 0x0004;
+ }
+}
diff --git a/src/fs/mod.rs b/src/fs/mod.rs
index f371830..90153e5 100644
--- a/src/fs/mod.rs
+++ b/src/fs/mod.rs
@@ -2,5 +2,7 @@
//!
//! Contains modules for the Virtual File System (vfs) and an ext2 implementations
+mod ext2;
pub mod node;
pub mod path;
+pub mod vfs;
diff --git a/src/fs/vfs.rs b/src/fs/vfs.rs
new file mode 100644
index 0000000..31f1e6a
--- /dev/null
+++ b/src/fs/vfs.rs
@@ -0,0 +1,3 @@
+//! Virtual File System (vfs)
+//!
+//! Interface between the file system and the kernel/user
--
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