574 lines
20 KiB
Rust
574 lines
20 KiB
Rust
// SPDX-License-Identifier: MPL-2.0
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use alloc::str;
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use ostd::task::Task;
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use super::Path;
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use crate::{
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fs::{
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file_table::{FileDesc, get_file_fast},
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path::MountNamespace,
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utils::{InodeType, PATH_MAX, SYMLINKS_MAX, SymbolicLink},
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},
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prelude::*,
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process::posix_thread::AsThreadLocal,
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};
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/// The file descriptor of the current working directory.
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pub const AT_FDCWD: FileDesc = -100;
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/// File system resolver.
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#[derive(Debug, Clone)]
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pub struct PathResolver {
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root: Path,
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cwd: Path,
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}
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impl PathResolver {
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/// Creates a new `PathResolver` with the given `root` and `cwd`.
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pub(super) fn new(root: Path, cwd: Path) -> Self {
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Self { root, cwd }
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}
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/// Gets the path of the root directory.
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pub fn root(&self) -> &Path {
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&self.root
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}
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/// Gets the path of the current working directory.
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pub fn cwd(&self) -> &Path {
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&self.cwd
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}
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/// Sets the current working directory to the given `path`.
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pub fn set_cwd(&mut self, path: Path) {
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self.cwd = path;
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}
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/// Sets the root directory to the given `path`.
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pub fn set_root(&mut self, path: Path) {
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self.root = path;
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}
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/// Switches the `PathResolver` to the given mount namespace.
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///
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/// If the target namespace already owns both the current root and working directory's
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/// mount nodes, the operation is a no-op and returns immediately.
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///
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/// Otherwise, the method will change both the `cwd` and `root` to their corresponding
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/// `Path`s within the new `MountNamespace`.
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//
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// FIXME: This cannot fail if we clone mount namespaces and update resolvers in an atomic way.
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// We currently leak this error to userspace, which is not a correct behavior.
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pub fn switch_to_mnt_ns(&mut self, mnt_ns: &Arc<MountNamespace>) -> Result<()> {
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if mnt_ns.owns(self.root.mount_node()) && mnt_ns.owns(self.cwd.mount_node()) {
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return Ok(());
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}
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let new_root = self.root.find_corresponding_mount(mnt_ns).ok_or_else(|| {
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Error::with_message(
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Errno::EINVAL,
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"the root directory does not exist in the target mount namespace",
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)
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})?;
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let new_cwd = self.cwd.find_corresponding_mount(mnt_ns).ok_or_else(|| {
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Error::with_message(
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Errno::EINVAL,
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"the current working directory does not exist in the target mount namespace",
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)
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})?;
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self.root = new_root;
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self.cwd = new_cwd;
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Ok(())
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}
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/// Lookups the target `Path` according to the `fs_path`.
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///
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/// Symlinks are always followed.
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pub fn lookup(&self, fs_path: &FsPath) -> Result<Path> {
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self.lookup_unresolved(fs_path)?.into_path()
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}
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/// Lookups the target `Path` according to the `fs_path`.
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///
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/// If the last component is a symlink, it will not be followed.
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pub fn lookup_no_follow(&self, fs_path: &FsPath) -> Result<Path> {
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self.lookup_unresolved_no_follow(fs_path)?.into_path()
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}
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/// Lookups the target `Path` according to the `fs_path` and leaves
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/// the result unresolved.
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///
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/// An unresolved result may indicate either successful full-path resolution,
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/// or resolution stopping at a parent path when the target doesn't exist
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/// but its parent does.
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///
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/// Symlinks are always followed.
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pub fn lookup_unresolved(&self, fs_path: &FsPath) -> Result<LookupResult> {
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self.lookup_inner(fs_path, true)
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}
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/// Lookups the target `Path` according to the `fs_path` and leaves
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/// the result unresolved.
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///
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/// An unresolved result may indicate either successful full-path resolution,
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/// or resolution stopping at a parent path when the target doesn't exist
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/// but its parent does.
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///
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/// If the last component is a symlink, it will not be followed.
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pub fn lookup_unresolved_no_follow(&self, fs_path: &FsPath) -> Result<LookupResult> {
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self.lookup_inner(fs_path, false)
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}
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fn lookup_inner(&self, fs_path: &FsPath, follow_tail_link: bool) -> Result<LookupResult> {
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let lookup_res = match fs_path.inner {
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FsPathInner::Absolute(path) => {
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self.lookup_from_parent(&self.root, path.trim_start_matches('/'), follow_tail_link)?
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}
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FsPathInner::CwdRelative(path) => {
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self.lookup_from_parent(&self.cwd, path, follow_tail_link)?
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}
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FsPathInner::Cwd => LookupResult::Resolved(self.cwd.clone()),
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FsPathInner::FdRelative(fd, path) => {
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let task = Task::current().unwrap();
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let mut file_table = task.as_thread_local().unwrap().borrow_file_table_mut();
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let file = get_file_fast!(&mut file_table, fd);
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let parent = file.as_inode_handle_or_err()?.path();
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self.lookup_from_parent(parent, path, follow_tail_link)?
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}
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FsPathInner::Fd(fd) => {
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let task = Task::current().unwrap();
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let mut file_table = task.as_thread_local().unwrap().borrow_file_table_mut();
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let file = get_file_fast!(&mut file_table, fd);
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LookupResult::Resolved(file.path().clone())
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}
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};
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Ok(lookup_res)
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}
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/// Lookups the target path according to the parent directory path.
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///
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/// The length of `path` cannot exceed `PATH_MAX`.
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/// If `path` ends with `/`, then the returned inode must be a directory inode.
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///
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/// While looking up the path, symbolic links will be followed for
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/// at most `SYMLINKS_MAX` times.
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///
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/// If `follow_tail_link` is true and the trailing component is a symlink,
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/// it will be followed.
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/// Symlinks in earlier components of the path will always be followed.
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#[expect(clippy::redundant_closure)]
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fn lookup_from_parent(
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&self,
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parent: &Path,
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relative_path: &str,
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follow_tail_link: bool,
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) -> Result<LookupResult> {
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debug_assert!(!relative_path.starts_with('/'));
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if relative_path.len() > PATH_MAX {
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return_errno_with_message!(Errno::ENAMETOOLONG, "the path is too long");
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}
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if relative_path.is_empty() {
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return Ok(LookupResult::Resolved(parent.clone()));
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}
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// To handle symlinks
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let mut link_path_opt = None;
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let mut follows = 0;
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// Initialize the first path and the relative path
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let (mut current_path, mut relative_path) = (parent.clone(), relative_path);
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while !relative_path.is_empty() {
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let (next_name, path_remain, target_is_dir) =
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if let Some((prefix, suffix)) = relative_path.split_once('/') {
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let suffix = suffix.trim_start_matches('/');
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(prefix, suffix, true)
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} else {
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(relative_path, "", false)
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};
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// Iterate next path
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let next_is_tail = path_remain.is_empty();
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let next_path = match current_path.lookup(next_name) {
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Ok(child) => child,
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Err(e) => {
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if next_is_tail && e.error() == Errno::ENOENT {
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return Ok(LookupResult::AtParent(LookupParentResult::new(
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current_path,
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next_name.to_string(),
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target_is_dir,
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)));
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}
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return Err(e);
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}
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};
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let next_type = next_path.type_();
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// If next inode is a symlink, follow symlinks at most `SYMLINKS_MAX` times.
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if next_type == InodeType::SymLink && (follow_tail_link || !next_is_tail) {
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if follows >= SYMLINKS_MAX {
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return_errno_with_message!(Errno::ELOOP, "there are too many symlinks");
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}
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let read_link_res = next_path.inode().read_link()?;
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match read_link_res {
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SymbolicLink::Plain(mut tmp_link_path) => {
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let link_path_remain = {
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if tmp_link_path.is_empty() {
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return_errno_with_message!(
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Errno::ENOENT,
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"the symlink path is empty"
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);
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}
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if !next_is_tail {
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tmp_link_path += "/";
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tmp_link_path += path_remain;
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} else if target_is_dir {
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tmp_link_path += "/";
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}
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tmp_link_path
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};
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// Change the path and relative path according to symlink
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if link_path_remain.starts_with('/') {
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current_path = self.root.clone();
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}
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let link_path = link_path_opt.get_or_insert_with(|| String::new());
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link_path.clear();
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link_path.push_str(link_path_remain.trim_start_matches('/'));
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relative_path = link_path;
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follows += 1;
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}
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SymbolicLink::Path(path) => {
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current_path = path;
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relative_path = path_remain;
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follows += 1;
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}
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}
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} else {
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// If path ends with `/`, the inode must be a directory
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if target_is_dir && next_type != InodeType::Dir {
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return_errno_with_message!(Errno::ENOTDIR, "the inode is not a directory");
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}
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current_path = next_path;
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relative_path = path_remain;
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}
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}
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Ok(LookupResult::Resolved(current_path))
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}
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}
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/// Path in the file system.
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#[derive(Debug)]
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pub struct FsPath<'a> {
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inner: FsPathInner<'a>,
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}
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#[derive(Debug)]
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enum FsPathInner<'a> {
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// Absolute path
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Absolute(&'a str),
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// Path is relative to `Cwd`
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CwdRelative(&'a str),
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// Current working directory
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Cwd,
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// Path is relative to the directory fd
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FdRelative(FileDesc, &'a str),
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// Fd
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Fd(FileDesc),
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}
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impl<'a> FsPath<'a> {
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/// Creates a new `FsPath` from the given `dirfd`.
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///
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/// If the FD is not valid (i.e., it's negative and it's not [`AT_FDCWD`]), an error will be
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/// returned.
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pub fn from_fd(dirfd: FileDesc) -> Result<Self> {
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let fs_path_inner = if dirfd >= 0 {
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FsPathInner::Fd(dirfd)
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} else if dirfd == AT_FDCWD {
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FsPathInner::Cwd
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} else {
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return_errno_with_message!(Errno::EBADF, "the dirfd is invalid");
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};
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Ok(Self {
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inner: fs_path_inner,
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})
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}
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/// Creates a new `FsPath` from the given `dirfd` and `path`.
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///
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/// If the FD is not valid (i.e., it's negative and it's not [`AT_FDCWD`]) or the path is empty
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/// or too long, an error will be returned.
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pub fn from_fd_and_path(dirfd: FileDesc, path: &'a str) -> Result<Self> {
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if path.is_empty() {
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return_errno_with_message!(Errno::ENOENT, "the path is empty")
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}
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if path.len() > PATH_MAX {
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return_errno_with_message!(Errno::ENAMETOOLONG, "the path is too long");
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}
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let fs_path_inner = if path.starts_with('/') {
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FsPathInner::Absolute(path)
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} else if dirfd >= 0 {
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FsPathInner::FdRelative(dirfd, path)
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} else if dirfd == AT_FDCWD {
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FsPathInner::CwdRelative(path)
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} else {
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return_errno_with_message!(Errno::EBADF, "the dirfd is invalid");
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};
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Ok(Self {
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inner: fs_path_inner,
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})
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}
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}
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impl<'a> TryFrom<&'a str> for FsPath<'a> {
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type Error = crate::error::Error;
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fn try_from(path: &'a str) -> Result<FsPath<'a>> {
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FsPath::from_fd_and_path(AT_FDCWD, path)
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}
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}
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// A result type for lookup operations.
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pub enum LookupResult {
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/// The entire path was resolved to a final `Path`.
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Resolved(Path),
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/// The path resolution stopped at a parent directory.
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AtParent(LookupParentResult),
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}
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impl LookupResult {
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fn into_path(self) -> Result<Path> {
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match self {
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LookupResult::Resolved(target) => Ok(target),
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LookupResult::AtParent(_) => Err(Error::with_message(
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Errno::ENOENT,
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"path resolution did not reach the final target",
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)),
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}
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}
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/// Consumes the `LookupResult` and returns the parent path and the unresolved file name.
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///
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/// If the path was resolved or the unresolved name was expected to be a directory, an error
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/// will be returned.
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pub fn into_parent_and_filename(self) -> Result<(Path, String)> {
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let LookupResult::AtParent(res) = self else {
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return_errno_with_message!(Errno::EEXIST, "the path already exists");
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};
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res.into_parent_and_filename()
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}
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/// Consumes the `LookupResult` and returns the parent path and the unresolved name.
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///
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/// If the path was resolved, an error will be returned.
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pub fn into_parent_and_basename(self) -> Result<(Path, String)> {
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let LookupResult::AtParent(res) = self else {
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return_errno_with_message!(Errno::EEXIST, "the path already exists");
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};
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Ok(res.into_parent_and_basename())
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}
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}
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/// A result that contains information about a path lookup that stopped
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/// at a parent directory.
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pub struct LookupParentResult {
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/// The path of the parent directory where resolution stopped.
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parent: Path,
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/// The remaining unresolved component name.
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unresolved_name: String,
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/// Indicates whether the target was expected to be a directory.
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target_is_dir: bool,
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}
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impl LookupParentResult {
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fn new(parent: Path, unresolved_name: String, target_is_dir: bool) -> Self {
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Self {
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parent,
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unresolved_name,
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target_is_dir,
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}
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}
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/// Returns true if the target was expected to be a directory.
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pub fn target_is_dir(&self) -> bool {
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self.target_is_dir
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}
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/// Consumes the `LookupParentResult` and returns the parent path and the unresolved file name.
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///
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/// If the unresolved name was expected to be a directory, an error will be returned.
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pub fn into_parent_and_filename(self) -> Result<(Path, String)> {
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if self.target_is_dir {
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return_errno_with_message!(Errno::ENOENT, "the path is a directory");
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}
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Ok((self.parent, self.unresolved_name))
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}
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/// Consumes the `LookupParentResult` and returns the parent path and the unresolved name.
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pub fn into_parent_and_basename(self) -> (Path, String) {
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(self.parent, self.unresolved_name)
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}
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}
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/// Utilities to split a string into its path components.
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pub trait SplitPath {
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/// Splits a path into the parent directory name and the final component name, which is
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/// expected to be a file (not a directory).
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///
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/// If the final component refers to a directory, an error will be returned. Aside from the
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/// constraint on the final component, this is similar to [`Self::split_dirname_and_basename`].
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fn split_dirname_and_filename(&self) -> Result<(&Self, &Self)>;
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/// Splits a path into the parent directory name and the final component name.
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///
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/// This behaves in a similar way to the POSIX C functions [`dirname()` and
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/// `basename()`](https://man7.org/linux/man-pages/man3/basename.3.html). Trailing slashes
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/// (`/`) are trimmed from returned names unless the name refers to the root directory. In that
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/// case, the name contains a single slash.
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///
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/// If the original path is an empty string, an error will be returned.
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///
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/// If the original path directly points to the root directory (e.g., `/` or `//`, but not `/.`
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/// or `/./`), an error will be returned.
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fn split_dirname_and_basename(&self) -> Result<(&Self, &Self)>;
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}
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impl SplitPath for str {
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fn split_dirname_and_filename(&self) -> Result<(&Self, &Self)> {
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if self.ends_with('/') {
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return_errno_with_message!(Errno::EISDIR, "the path is a directory");
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}
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self.split_dirname_and_basename()
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}
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fn split_dirname_and_basename(&self) -> Result<(&Self, &Self)> {
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if self.is_empty() {
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return_errno_with_message!(Errno::ENOENT, "the path is empty");
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}
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let trimmed = self.trim_end_matches('/');
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if trimmed.is_empty() {
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return_errno_with_message!(Errno::EBUSY, "the path is the root directory");
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}
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if let Some(pos) = trimmed.rfind('/') {
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let dirname = trimmed[..pos].trim_end_matches('/');
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Ok((
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if dirname.is_empty() { "/" } else { dirname },
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&trimmed[pos + 1..],
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))
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} else {
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Ok((".", trimmed))
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}
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}
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}
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#[cfg(ktest)]
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mod test {
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use ostd::prelude::ktest;
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use super::*;
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type SplitResult = core::result::Result<(&'static str, &'static str), Errno>;
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#[track_caller]
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fn assert_split_results(
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cases: &Vec<(&'static str, SplitResult)>,
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split: impl Fn(&str) -> Result<(&str, &str)>,
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) {
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for case in cases.iter() {
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let result = split(case.0);
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assert_eq!(
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result.map_err(|err| err.error()),
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case.1,
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"splitting '{}' failed",
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case.0
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);
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}
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}
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#[ktest]
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fn path_split_filename() {
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let cases = vec![
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("", Err(Errno::ENOENT)),
|
|
("/", Err(Errno::EISDIR)),
|
|
("///", Err(Errno::EISDIR)),
|
|
("///.", Ok(("/", "."))),
|
|
("//./", Err(Errno::EISDIR)),
|
|
("a", Ok((".", "a"))),
|
|
("/a", Ok(("/", "a"))),
|
|
("b/a", Ok(("b", "a"))),
|
|
("/b/a", Ok(("/b", "a"))),
|
|
("a", Ok((".", "a"))),
|
|
("//a", Ok(("/", "a"))),
|
|
("b//a", Ok(("b", "a"))),
|
|
("//b//a", Ok(("//b", "a"))),
|
|
("a/", Err(Errno::EISDIR)),
|
|
("/a/", Err(Errno::EISDIR)),
|
|
("b/a/", Err(Errno::EISDIR)),
|
|
("/b/a/", Err(Errno::EISDIR)),
|
|
("a//", Err(Errno::EISDIR)),
|
|
("/a//", Err(Errno::EISDIR)),
|
|
("b/a//", Err(Errno::EISDIR)),
|
|
("/b/a//", Err(Errno::EISDIR)),
|
|
(" a ", Ok((".", " a "))),
|
|
(" //a ", Ok((" ", "a "))),
|
|
(" b//a ", Ok((" b", "a "))),
|
|
(" //b//a ", Ok((" //b", "a "))),
|
|
(" a/ ", Ok((" a", " "))),
|
|
(" //a/ ", Ok((" //a", " "))),
|
|
(" b//a/ ", Ok((" b//a", " "))),
|
|
(" //b//a/ ", Ok((" //b//a", " "))),
|
|
];
|
|
assert_split_results(&cases, SplitPath::split_dirname_and_filename);
|
|
}
|
|
|
|
#[ktest]
|
|
fn path_split_basename() {
|
|
let cases = vec![
|
|
("", Err(Errno::ENOENT)),
|
|
("/", Err(Errno::EBUSY)),
|
|
("///", Err(Errno::EBUSY)),
|
|
("///.", Ok(("/", "."))),
|
|
("//./", Ok(("/", "."))),
|
|
("a", Ok((".", "a"))),
|
|
("/a", Ok(("/", "a"))),
|
|
("b/a", Ok(("b", "a"))),
|
|
("/b/a", Ok(("/b", "a"))),
|
|
("a", Ok((".", "a"))),
|
|
("//a", Ok(("/", "a"))),
|
|
("b//a", Ok(("b", "a"))),
|
|
("//b//a", Ok(("//b", "a"))),
|
|
("a/", Ok((".", "a"))),
|
|
("/a/", Ok(("/", "a"))),
|
|
("b/a/", Ok(("b", "a"))),
|
|
("/b/a/", Ok(("/b", "a"))),
|
|
("a//", Ok((".", "a"))),
|
|
("/a//", Ok(("/", "a"))),
|
|
("b/a//", Ok(("b", "a"))),
|
|
("/b/a//", Ok(("/b", "a"))),
|
|
(" a ", Ok((".", " a "))),
|
|
(" //a ", Ok((" ", "a "))),
|
|
(" b//a ", Ok((" b", "a "))),
|
|
(" //b//a ", Ok((" //b", "a "))),
|
|
(" a/ ", Ok((" a", " "))),
|
|
(" //a/ ", Ok((" //a", " "))),
|
|
(" b//a/ ", Ok((" b//a", " "))),
|
|
(" //b//a/ ", Ok((" //b//a", " "))),
|
|
];
|
|
assert_split_results(&cases, SplitPath::split_dirname_and_basename);
|
|
}
|
|
}
|