1//! The [`pidfd_getfd`] function and supporting types.
2
3#![allow(unsafe_code)]
4use crate::fd::OwnedFd;
5use crate::{backend, io};
6use backend::fd::{AsFd, RawFd};
7
8/// Raw file descriptor in another process.
9///
10/// A distinct type alias is used here to inform the user that normal file
11/// descriptors from the calling process should not be used. The provided file
12/// descriptor is used by the kernel as the index into the file descriptor
13/// table of an entirely different process.
14pub type ForeignRawFd = RawFd;
15
16bitflags::bitflags! {
17 /// All flags are reserved for future use.
18 #[repr(transparent)]
19 #[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
20 pub struct PidfdGetfdFlags: backend::c::c_uint {
21 /// <https://docs.rs/bitflags/*/bitflags/#externally-defined-flags>
22 const _ = !0;
23 }
24}
25
26/// `syscall(SYS_pidfd_getfd, pidfd, flags)`—Obtain a duplicate of another
27/// process' file descriptor.
28///
29/// # References
30/// - [Linux]
31///
32/// # Warning
33///
34/// This function is generally safe for the calling process, but it can impact
35/// the target process in unexpected ways. If you want to ensure that Rust I/O
36/// safety assumptions continue to hold in the target process, then the target
37/// process must have communicated the file description number to the calling
38/// process from a value of a type that implements `AsRawFd`, and the target
39/// process must not drop that value until after the calling process has
40/// returned from `pidfd_getfd`.
41///
42/// When `pidfd_getfd` is used to debug the target, or the target is not a Rust
43/// application, or `pidfd_getfd` is used in any other way, then extra care
44/// should be taken to avoid unexpected behaviour or crashes.
45///
46/// For further details, see the references above.
47///
48/// [Linux]: https://man7.org/linux/man-pages/man2/pidfd_getfd.2.html
49#[inline]
50pub fn pidfd_getfd<Fd: AsFd>(
51 pidfd: Fd,
52 targetfd: ForeignRawFd,
53 flags: PidfdGetfdFlags,
54) -> io::Result<OwnedFd> {
55 backend::process::syscalls::pidfd_getfd(pidfd.as_fd(), targetfd, flags)
56}
57