lxutil/unix/mod.rs
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// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.
// UNSAFETY: Calling libc file APIs.
#![expect(unsafe_code)]
#![expect(clippy::undocumented_unsafe_blocks)]
pub(crate) mod path;
mod util;
use crate::SetAttributes;
use std::ffi;
use std::mem;
use std::os::unix::prelude::*;
use std::path::Path;
// Unix implementation of LxVolume.
// See crate::LxVolume for more detailed comments.
pub struct LxVolume {
root: std::fs::File,
}
impl LxVolume {
pub fn new(root_path: &Path, _options: &super::LxVolumeOptions) -> lx::Result<Self> {
let path = util::path_to_cstr(root_path)?;
// SAFETY: Calling C API as documented, with no special requirements.
unsafe {
// Open a file descriptor to the root to use with "*at" functions.
let fd = util::check_lx_errno(libc::open(
path.as_ptr(),
libc::O_RDONLY | libc::O_DIRECTORY,
))?;
Ok(Self {
root: std::fs::File::from_raw_fd(fd),
})
}
}
pub fn supports_stable_file_id(&self) -> bool {
true
}
pub fn lstat(&self, path: &Path) -> lx::Result<lx::Stat> {
assert!(path.is_relative());
let path = util::path_to_cstr(path)?;
// SAFETY: Calling C API as documented, with no special requirements.
let stat = unsafe {
let mut stat = mem::zeroed();
util::check_lx_errno(libc::fstatat(
self.root.as_raw_fd(),
path.as_ptr(),
&mut stat,
libc::AT_SYMLINK_NOFOLLOW | libc::AT_EMPTY_PATH,
))?;
stat
};
Ok(util::libc_stat_to_lx_stat(stat))
}
pub fn set_attr(&self, path: &Path, attr: SetAttributes) -> lx::Result<()> {
util::set_attr(&self.root, Some(path), &attr)
}
pub fn set_attr_stat(&self, path: &Path, attr: SetAttributes) -> lx::Result<lx::Stat> {
util::set_attr(&self.root, Some(path), &attr)?;
self.lstat(path)
}
pub fn open(
&self,
path: &Path,
flags: i32,
options: Option<super::LxCreateOptions>,
) -> lx::Result<LxFile> {
assert!(path.is_relative());
let fd = util::openat(&self.root, path, flags, options)?;
Ok(LxFile {
fd,
enumerator: None,
})
}
pub fn mkdir(&self, path: &Path, options: super::LxCreateOptions) -> lx::Result<()> {
assert!(path.is_relative());
let path = util::path_to_cstr(path)?;
// SAFETY: Calling C API as documented, with no special requirements.
unsafe {
util::check_lx_errno(libc::mkdirat(
self.root.as_raw_fd(),
path.as_ptr(),
options.mode,
))?;
}
Ok(())
}
pub fn mkdir_stat(&self, path: &Path, options: super::LxCreateOptions) -> lx::Result<lx::Stat> {
self.mkdir(path, options)?;
self.lstat(path)
}
// The options are entirely ignored on Unix, because uid/gid are never used, and mode isn't
// used for symlinks.
pub fn symlink(
&self,
path: &Path,
target: &lx::LxStr,
_: super::LxCreateOptions,
) -> lx::Result<()> {
assert!(path.is_relative());
let path = util::path_to_cstr(path)?;
let target = util::create_cstr(target.as_bytes())?;
// SAFETY: Calling C API as documented, with no special requirements.
unsafe {
util::check_lx_errno(libc::symlinkat(
target.as_ptr(),
self.root.as_raw_fd(),
path.as_ptr(),
))?;
}
Ok(())
}
pub fn symlink_stat(
&self,
path: &Path,
target: &lx::LxStr,
options: super::LxCreateOptions,
) -> lx::Result<lx::Stat> {
self.symlink(path, target, options)?;
self.lstat(path)
}
pub fn read_link(&self, path: &Path) -> lx::Result<lx::LxString> {
assert!(path.is_relative());
let mut buffer = [0u8; libc::PATH_MAX as usize];
let path = util::path_to_cstr(path)?;
// SAFETY: Calling C API as documented, with no special requirements.
let size = unsafe {
util::check_lx_errno(libc::readlinkat(
self.root.as_raw_fd(),
path.as_ptr(),
buffer.as_mut_ptr().cast(),
buffer.len(),
))?
};
// Size is guaranteed to be positive after check_lx_errno.
Ok(lx::LxString::from_vec(Vec::from(&buffer[..size as usize])))
}
pub fn unlink(&self, path: &Path, flags: i32) -> lx::Result<()> {
assert!(path.is_relative());
let path = util::path_to_cstr(path)?;
// SAFETY: Calling C API as documented, with no special requirements.
unsafe {
util::check_lx_errno(libc::unlinkat(self.root.as_raw_fd(), path.as_ptr(), flags))?;
}
Ok(())
}
pub fn mknod(
&self,
path: &Path,
options: super::LxCreateOptions,
device_id: lx::dev_t,
) -> lx::Result<()> {
assert!(path.is_relative());
let path = util::path_to_cstr(path)?;
// SAFETY: Calling C API as documented, with no special requirements.
unsafe {
util::check_lx_errno(libc::mknodat(
self.root.as_raw_fd(),
path.as_ptr(),
options.mode,
device_id as u64,
))?;
}
Ok(())
}
pub fn mknod_stat(
&self,
path: &Path,
options: super::LxCreateOptions,
device_id: lx::dev_t,
) -> lx::Result<lx::Stat> {
self.mknod(path, options, device_id)?;
self.lstat(path)
}
pub fn rename(&self, path: &Path, new_path: &Path, flags: u32) -> lx::Result<()> {
assert!(path.is_relative());
assert!(new_path.is_relative());
let path = util::path_to_cstr(path)?;
let new_path = util::path_to_cstr(new_path)?;
// renameat2 does not have a wrapper in musl, though it does in glibc. Call it using syscall directly instead.
// SAFETY: Our arguments are valid for this syscall. We are passing arguments in the
// correct order and as the correct types. We are casting the return value to the correct type.
unsafe {
util::check_lx_errno(libc::syscall(
libc::SYS_renameat2,
self.root.as_raw_fd(),
path.as_ptr(),
self.root.as_raw_fd(),
new_path.as_ptr(),
flags,
) as libc::c_int)?;
}
Ok(())
}
pub fn link(&self, path: &Path, new_path: &Path) -> lx::Result<()> {
assert!(path.is_relative());
assert!(new_path.is_relative());
let path = util::path_to_cstr(path)?;
let new_path = util::path_to_cstr(new_path)?;
// SAFETY: Calling C API as documented, with no special requirements.
unsafe {
util::check_lx_errno(libc::linkat(
self.root.as_raw_fd(),
path.as_ptr(),
self.root.as_raw_fd(),
new_path.as_ptr(),
0,
))?;
}
Ok(())
}
pub fn link_stat(&self, path: &Path, new_path: &Path) -> lx::Result<lx::Stat> {
self.link(path, new_path)?;
self.lstat(new_path)
}
pub fn stat_fs(&self, path: &Path) -> lx::Result<lx::StatFs> {
assert!(path.is_relative());
let path = self.full_path(path)?;
// SAFETY: Calling C API as documented, with no special requirements.
let stat_fs = unsafe {
let mut stat_fs = mem::zeroed();
util::check_lx_errno(libc::statfs(path.as_ptr(), &mut stat_fs))?;
stat_fs
};
Ok(util::libc_stat_fs_to_lx_stat_fs(stat_fs))
}
pub fn set_xattr(
&self,
path: &Path,
name: &lx::LxStr,
value: &[u8],
flags: i32,
) -> lx::Result<()> {
assert!(path.is_relative());
// There is no *at version of the xattr APIs.
let path = self.full_path(path)?;
let name = util::create_cstr(name.as_bytes())?;
// SAFETY: Calling C API as documented, with no special requirements.
unsafe {
util::check_lx_errno(libc::lsetxattr(
path.as_ptr(),
name.as_ptr(),
value.as_ptr().cast::<ffi::c_void>(),
value.len(),
flags,
))?;
}
Ok(())
}
pub fn get_xattr(
&self,
path: &Path,
name: &lx::LxStr,
value: Option<&mut [u8]>,
) -> lx::Result<usize> {
assert!(path.is_relative());
// There is no *at version of the xattr APIs.
let path = self.full_path(path)?;
let name = util::create_cstr(name.as_bytes())?;
// Set the pointer to NULL if no value buffer is provided, to query the attribute's size.
let (value_ptr, size) = if let Some(value) = value {
(value.as_mut_ptr(), value.len())
} else {
(std::ptr::null_mut(), 0)
};
// SAFETY: Calling C API as documented, with no special requirements.
let size = unsafe {
util::check_lx_errno(libc::lgetxattr(
path.as_ptr(),
name.as_ptr(),
value_ptr.cast::<ffi::c_void>(),
size,
))?
};
// Size is guaranteed positive after the check.
Ok(size as usize)
}
pub fn list_xattr(&self, path: &Path, list: Option<&mut [u8]>) -> lx::Result<usize> {
assert!(path.is_relative());
// There is no *at version of the xattr APIs.
let path = self.full_path(path)?;
// Set the list pointer to NULL if no list buffer was provided, to query the size.
let (list_ptr, size) = if let Some(list) = list {
(list.as_mut_ptr(), list.len())
} else {
(std::ptr::null_mut(), 0)
};
// SAFETY: Calling C API as documented, with no special requirements.
let size = unsafe {
util::check_lx_errno(libc::llistxattr(path.as_ptr(), list_ptr.cast(), size))?
};
// Size is guaranteed positive after the check.
Ok(size as usize)
}
pub fn remove_xattr(&self, path: &Path, name: &lx::LxStr) -> lx::Result<()> {
assert!(path.is_relative());
// There is no *at version of the xattr APIs.
let path = self.full_path(path)?;
let name = util::create_cstr(name.as_bytes())?;
// SAFETY: Calling C API as documented, with no special requirements.
unsafe {
util::check_lx_errno(libc::lremovexattr(path.as_ptr(), name.as_ptr()))?;
}
Ok(())
}
fn full_path(&self, path: &Path) -> lx::Result<ffi::CString> {
let mut full_path = util::get_fd_path(&self.root)?;
full_path.push(path);
util::path_to_cstr(&full_path)
}
}
// Unix implementation of LxFile.
// See crate::LxFile for more detailed comments.
pub struct LxFile {
fd: std::fs::File,
enumerator: Option<util::DirectoryEnumerator>,
}
impl LxFile {
pub fn fstat(&self) -> lx::Result<lx::Stat> {
// SAFETY: Calling C API as documented, with no special requirements.
let stat = unsafe {
let mut stat = mem::zeroed();
util::check_lx_errno(libc::fstat(self.fd.as_raw_fd(), &mut stat))?;
stat
};
Ok(util::libc_stat_to_lx_stat(stat))
}
pub fn set_attr(&self, attr: SetAttributes) -> lx::Result<()> {
util::set_attr(&self.fd, None, &attr)
}
pub fn pread(&self, buffer: &mut [u8], offset: lx::off_t) -> lx::Result<usize> {
// SAFETY: Calling C API as documented, with no special requirements.
let size = unsafe {
util::check_lx_errno(libc::pread(
self.fd.as_raw_fd(),
buffer.as_mut_ptr().cast::<ffi::c_void>(),
buffer.len(),
offset,
))?
};
// After checking for error, size is guaranteed positive.
Ok(size as usize)
}
pub fn pwrite(&self, buffer: &[u8], offset: lx::off_t, _: lx::uid_t) -> lx::Result<usize> {
// Linux will clear the set-user-ID and set-group-ID version on write, so unlike the
// Windows version, that doesn't need to be done here explicitly.
// SAFETY: Calling C API as documented, with no special requirements.
let size = unsafe {
util::check_lx_errno(libc::pwrite(
self.fd.as_raw_fd(),
buffer.as_ptr() as *mut ffi::c_void,
buffer.len(),
offset,
))?
};
// After checking for error, size is guaranteed positive.
Ok(size as usize)
}
pub fn read_dir<F>(&mut self, offset: lx::off_t, mut callback: F) -> lx::Result<()>
where
F: FnMut(lx::DirEntry) -> lx::Result<bool>,
{
if self.enumerator.is_none() {
// The fd must be cloned because fdopendir takes ownership of the fd. This could be
// avoided by moving the fd out of self.fd.
// TODO: Use an enum with an "invalid" state to allow this.
self.enumerator = Some(util::DirectoryEnumerator::new(self.fd.try_clone()?)?);
}
let enumerator = self.enumerator.as_mut().unwrap();
enumerator.seek(offset);
for entry in enumerator {
let result = callback(entry?)?;
if !result {
break;
}
}
Ok(())
}
pub fn fsync(&self, data_only: bool) -> lx::Result<()> {
// SAFETY: Calling C APIs as documented, with no special requirements.
unsafe {
if data_only {
util::check_lx_errno(libc::fdatasync(self.fd.as_raw_fd()))?;
} else {
util::check_lx_errno(libc::fsync(self.fd.as_raw_fd()))?;
}
}
Ok(())
}
}