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//! Path canonicalization using `/proc/self/fd`.
use super::procfs::get_path_from_proc_self_fd;
use crate::fs::{manually, open_beneath, FollowSymlinks, OpenOptions};
use std::{
fs, io,
os::unix::fs::OpenOptionsExt,
path::{Component, Path, PathBuf},
};
/// Implement `canonicalize` by using readlink on `/proc/self/fd/*`.
pub(crate) fn canonicalize_impl(start: &fs::File, path: &Path) -> io::Result<PathBuf> {
// Open the path with `O_PATH`. Use `read(true)` even though we don't need
// `read` permissions, because Rust's libstd requires an access mode, and
// Linux ignores `O_RDONLY` with `O_PATH`.
let result = open_beneath(
start,
path,
OpenOptions::new()
.read(true)
.follow(FollowSymlinks::Yes)
.custom_flags(libc::O_PATH),
);
// If that worked, call `readlink`.
match result {
Ok(file) => {
if let Ok(start_path) = get_path_from_proc_self_fd(start) {
if let Ok(file_path) = get_path_from_proc_self_fd(&file) {
if let Ok(canonical_path) = file_path.strip_prefix(start_path) {
#[cfg(racy_asserts)]
if canonical_path.as_os_str().is_empty() {
assert_eq!(
Component::CurDir.as_os_str(),
manually::canonicalize(start, path).unwrap()
);
} else {
assert_eq!(
canonical_path,
manually::canonicalize(start, path).unwrap()
);
}
let mut path_buf = canonical_path.to_path_buf();
// Replace "" with ".", since "" as a relative path is
// interpreted as an error.
if path_buf.as_os_str().is_empty() {
path_buf.push(Component::CurDir);
}
return Ok(path_buf);
}
}
}
}
Err(err) => match err.raw_os_error() {
// `ENOSYS` from `open_beneath` means `openat2` is unavailable
// and we should use a fallback.
Some(libc::ENOSYS) => (),
_ => return Err(err),
},
}
// Use a fallback.
manually::canonicalize(start, path)
}