forked from AbleOS/ableos
306 lines
8.6 KiB
Rust
306 lines
8.6 KiB
Rust
/*
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* Copyright (c) 2022, Umut İnan Erdoğan <umutinanerdogan@pm.me>
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*
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* SPDX-License-Identifier: MPL-2.0
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*/
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use core::cmp;
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use alloc::sync::{Arc, Weak};
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use hashbrown::HashMap;
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use lazy_static::lazy_static;
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use spin::Mutex;
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use super::{errors::FsError, FsResult as Result};
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use crate::{
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handle::{Handle, HandleResource},
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KERNEL_STATE,
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};
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/// The limit for symlink recursion. In POSIX, this is at least 8. In Linux, this is 40.
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const SYMLINK_RECURSION_LIMIT: u8 = 8;
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lazy_static! {
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pub static ref VFS: Mutex<VirtualFileSystem> = Default::default();
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}
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pub struct VirtualFileSystem {
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fs_nodes: HashMap<Handle, Arc<FsNode>>,
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root_node: Weak<FsNode>,
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root_handle: Option<Handle>,
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}
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impl VirtualFileSystem {
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/// Sets the VFS root to the given VFS node handle.
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pub fn set_root(&mut self, handle: Handle) -> Result<()> {
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let root_node = self.fs_node(handle).ok_or_else(|| FsError::NotFound)?;
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self.root_node = Arc::downgrade(&root_node);
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self.root_handle = Some(handle);
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Ok(())
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}
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/// Resolves the path to a handle. If the resulting node is a symlink,
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/// the symlink itself is returned. All symlinks but the resulting node
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/// are traversed.
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///
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/// Requires a mutable reference because internally it might open new VFS
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/// nodes while resolving the path.
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pub fn resolve<S: AsRef<str>>(&mut self, path: S) -> Result<Handle> {
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// TODO: caching
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let path = path.as_ref();
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if !path.starts_with('/') {
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// FIXME: use current process working directory for relative paths?
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Err(FsError::NotAbsolute)?;
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}
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let mut components = path.split_terminator('/');
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components.next(); // throw the empty string caused by the root /
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// will be initialised beforehand so okay to unwrap
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let mut resolved_node = self.root_handle.unwrap();
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// let mut symlink_recursion_level = 0;
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for component in components {
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// if symlink_recursion_level >= SYMLINK_RECURSION_LIMIT {
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// Err(FsError::Recursion)?;
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// }
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if component == "" {
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Err(FsError::InvalidPath)?;
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}
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// checked by previous iteration so okay to unwrap
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let parent = self.fs_node(resolved_node).unwrap();
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// TODO: permission checks
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// FIXME: find_dir checks that this is a directory already but
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// that's just more boilerplate in StorageDevice impls
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// we should probably check that here instead to reduce
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// required boilerplate
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// if !parent.is_dir() {
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// Err(FsError::NotADirectory)?;
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// }
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// FIXME: handle mount points
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// FIXME: handle symlinks
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resolved_node = parent.find_dir(self, component)?;
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}
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Ok(resolved_node)
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}
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pub fn add_fs_node(&mut self, fs_node: Arc<FsNode>) -> Handle {
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let handle = Handle::new(HandleResource::FsNode);
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self.fs_nodes.insert(handle, fs_node);
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handle
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}
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pub fn find_fs_node(&mut self, inode: usize, device_handle: Handle) -> Option<Handle> {
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self.fs_nodes.iter().find_map(|(handle, fs_node)| {
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if fs_node.inode == inode && fs_node.device_handle == device_handle {
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Some(*handle)
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} else {
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None
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}
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})
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}
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pub fn fs_node(&self, handle: Handle) -> Option<Arc<FsNode>> {
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self.fs_nodes.get(&handle).cloned()
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}
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pub fn root_node(&self) -> Arc<FsNode> {
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// okay to unwrap since this should never be called before init
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self.root_node.upgrade().unwrap()
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}
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}
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impl Default for VirtualFileSystem {
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fn default() -> Self {
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Self {
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fs_nodes: HashMap::new(),
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root_node: Weak::new(),
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root_handle: None,
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}
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}
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}
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/// A VFS node, that can either be a file or a directory.
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///
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/// VFS nodes are created whenever a file that doesn't have an open VFS node is
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/// opened. When there are no open file descriptors to a file, the associated
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/// VFS node is dropped.
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#[derive(Debug)]
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pub struct FsNode {
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flags: FsFlags,
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size: usize, // in bytes
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inode: usize, // implementation specific identifier for the node
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device_handle: Handle, // uniquely assigned device handle
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ptr: Weak<FsNode>, // used by mountpoints and symlinks
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// TODO: permissions mask
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// TODO: owning user/group
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}
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impl FsNode {
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pub fn new(
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flags: FsFlags,
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size: usize,
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inode: usize,
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device_handle: Handle,
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ptr: Weak<FsNode>,
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) -> Self {
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Self {
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flags,
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size,
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inode,
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device_handle,
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ptr,
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}
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}
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/// This method opens a new file descriptor for this VFS node.
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// TODO: make this take flags
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pub fn open(self: Arc<Self>) -> Result<Handle> {
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let mut state = KERNEL_STATE.lock();
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let handle = state.open_file_descriptor(self);
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Ok(handle)
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}
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/// This method reads from the VFS node without opening a new file
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/// descriptor. This is intended to be used internally, if you're trying to
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/// read a file then you probably want to read from a file descriptor.
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pub fn read(&self, offset: usize, size: usize, buffer: &mut Vec<u8>) -> Result<usize> {
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let state = KERNEL_STATE.lock();
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let device = state
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.storage_device(self.device_handle)
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.ok_or_else(|| FsError::InvalidDevice)?;
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if self.is_dir() {
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Err(FsError::IsDirectory)?;
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}
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if offset > self.size {
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Err(FsError::EndOfFile)?;
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}
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let readable_size = cmp::min(size, self.size - offset);
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device.read(self, offset, readable_size, buffer)?;
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Ok(readable_size)
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}
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/// This method writes to the VFS node without opening a new file
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/// descriptor. This is intended to be used internally, if you're trying to
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/// write to a file then you probably want to write to a file descriptor.
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pub fn write(&self, offset: usize, buffer: &[u8]) -> Result<()> {
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let state = KERNEL_STATE.lock();
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let device = state
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.storage_device(self.device_handle)
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.ok_or_else(|| FsError::InvalidDevice)?;
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device.write(self, offset, buffer)
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}
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pub fn read_dir(&self, index: usize) -> Result<DirectoryEntry> {
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let state = KERNEL_STATE.lock();
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let device = state
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.storage_device(self.device_handle)
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.ok_or_else(|| FsError::InvalidDevice)?;
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device.read_dir(self, index)
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}
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pub fn find_dir(&self, vfs: &mut VirtualFileSystem, name: &str) -> Result<Handle> {
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let state = KERNEL_STATE.lock();
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let device = state
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.storage_device(self.device_handle)
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.ok_or_else(|| FsError::InvalidDevice)?;
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device.find_dir(vfs, self, name)
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}
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pub fn directory(self: Arc<Self>) -> Option<Directory> {
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if self.is_dir() {
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Some(Directory::new(self))
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} else {
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None
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}
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}
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pub fn is_dir(&self) -> bool {
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(self.flags & FsFlags::DIRECTORY) == FsFlags::DIRECTORY
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}
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pub fn inode(&self) -> usize {
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self.inode
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}
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pub fn size(&self) -> usize {
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self.size
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}
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}
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impl Drop for FsNode {
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fn drop(&mut self) {
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trace!("dropping VFS node: {self:#?}");
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// TODO: flush to disk here
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}
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}
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bitflags! {
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/// Flags associated with VFS nodes and file descriptors
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///
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/// 0x00000MST \
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/// T is set to 0 for files, 1 for directories \
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/// S is set when the file is a symbolic link \
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/// M is set if the file is an active mount point
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pub struct FsFlags: u8 {
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const FILE = 0b00000000;
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const DIRECTORY = 0b00000001;
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const SYMBOLIC_LINK = 0b00000010;
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const MOUNT_POINT = 0b00000100;
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}
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}
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pub struct Directory {
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node: Arc<FsNode>,
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index: usize,
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}
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impl Directory {
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fn new(node: Arc<FsNode>) -> Self {
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Self { node, index: 0 }
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}
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}
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impl Iterator for Directory {
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type Item = DirectoryEntry;
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fn next(&mut self) -> Option<Self::Item> {
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let value = self.node.read_dir(self.index).ok();
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self.index += 1;
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value
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}
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}
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#[derive(Clone, Debug)]
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pub struct DirectoryEntry {
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name: String,
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node: Handle,
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}
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impl DirectoryEntry {
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pub(super) fn new(name: String, node: Handle) -> Self {
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Self { name, node }
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}
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pub fn name(&self) -> String {
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self.name.clone()
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}
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pub fn node(&self) -> Handle {
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self.node
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}
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}
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