1//! Linux-specific extensions to primitives in the [`std::process`] module.
2//!
3//! [`std::process`]: crate::process
4
5#![unstable(feature = "linux_pidfd", issue = "82971")]
6
7use crate::io::Result;
8use crate::os::unix::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, OwnedFd, RawFd};
9use crate::process::{self, ExitStatus};
10use crate::sealed::Sealed;
11#[cfg(not(doc))]
12use crate::sys::{fd::FileDesc, linux::pidfd::PidFd as InnerPidFd};
13use crate::sys_common::{AsInner, AsInnerMut, FromInner, IntoInner};
14
15#[cfg(doc)]
16struct InnerPidFd;
17
18/// This type represents a file descriptor that refers to a process.
19///
20/// A `PidFd` can be obtained by setting the corresponding option on [`Command`]
21/// with [`create_pidfd`]. Subsequently, the created pidfd can be retrieved
22/// from the [`Child`] by calling [`pidfd`] or [`into_pidfd`].
23///
24/// Example:
25/// ```no_run
26/// #![feature(linux_pidfd)]
27/// use std::os::linux::process::{CommandExt, ChildExt};
28/// use std::process::Command;
29///
30/// let mut child = Command::new("echo")
31/// .create_pidfd(true)
32/// .spawn()
33/// .expect("Failed to spawn child");
34///
35/// let pidfd = child
36/// .into_pidfd()
37/// .expect("Failed to retrieve pidfd");
38///
39/// // The file descriptor will be closed when `pidfd` is dropped.
40/// ```
41/// Refer to the man page of [`pidfd_open(2)`] for further details.
42///
43/// [`Command`]: process::Command
44/// [`create_pidfd`]: CommandExt::create_pidfd
45/// [`Child`]: process::Child
46/// [`pidfd`]: fn@ChildExt::pidfd
47/// [`into_pidfd`]: ChildExt::into_pidfd
48/// [`pidfd_open(2)`]: https://man7.org/linux/man-pages/man2/pidfd_open.2.html
49#[derive(Debug)]
50#[repr(transparent)]
51pub struct PidFd {
52 inner: InnerPidFd,
53}
54
55impl PidFd {
56 /// Forces the child process to exit.
57 ///
58 /// Unlike [`Child::kill`] it is possible to attempt to kill
59 /// reaped children since PidFd does not suffer from pid recycling
60 /// races. But doing so will return an Error.
61 ///
62 /// [`Child::kill`]: process::Child::kill
63 pub fn kill(&self) -> Result<()> {
64 self.inner.kill()
65 }
66
67 /// Waits for the child to exit completely, returning the status that it exited with.
68 ///
69 /// Unlike [`Child::wait`] it does not ensure that the stdin handle is closed.
70 /// Additionally it will not return an `ExitStatus` if the child
71 /// has already been reaped. Instead an error will be returned.
72 ///
73 /// [`Child::wait`]: process::Child::wait
74 pub fn wait(&self) -> Result<ExitStatus> {
75 self.inner.wait().map(FromInner::from_inner)
76 }
77
78 /// Attempts to collect the exit status of the child if it has already exited.
79 ///
80 /// Unlike [`Child::try_wait`] this method will return an Error
81 /// if the child has already been reaped.
82 ///
83 /// [`Child::try_wait`]: process::Child::try_wait
84 pub fn try_wait(&self) -> Result<Option<ExitStatus>> {
85 Ok(self.inner.try_wait()?.map(FromInner::from_inner))
86 }
87}
88
89impl AsInner<InnerPidFd> for PidFd {
90 #[inline]
91 fn as_inner(&self) -> &InnerPidFd {
92 &self.inner
93 }
94}
95
96impl FromInner<InnerPidFd> for PidFd {
97 fn from_inner(inner: InnerPidFd) -> PidFd {
98 PidFd { inner }
99 }
100}
101
102impl IntoInner<InnerPidFd> for PidFd {
103 fn into_inner(self) -> InnerPidFd {
104 self.inner
105 }
106}
107
108impl AsRawFd for PidFd {
109 #[inline]
110 fn as_raw_fd(&self) -> RawFd {
111 self.as_inner().as_inner().as_raw_fd()
112 }
113}
114
115impl FromRawFd for PidFd {
116 unsafe fn from_raw_fd(fd: RawFd) -> Self {
117 Self::from_inner(InnerPidFd::from_raw_fd(fd))
118 }
119}
120
121impl IntoRawFd for PidFd {
122 fn into_raw_fd(self) -> RawFd {
123 self.into_inner().into_inner().into_raw_fd()
124 }
125}
126
127impl AsFd for PidFd {
128 fn as_fd(&self) -> BorrowedFd<'_> {
129 self.as_inner().as_inner().as_fd()
130 }
131}
132
133impl From<OwnedFd> for PidFd {
134 fn from(fd: OwnedFd) -> Self {
135 Self::from_inner(InnerPidFd::from_inner(FileDesc::from_inner(fd)))
136 }
137}
138
139impl From<PidFd> for OwnedFd {
140 fn from(pid_fd: PidFd) -> Self {
141 pid_fd.into_inner().into_inner().into_inner()
142 }
143}
144
145/// Os-specific extensions for [`Child`]
146///
147/// [`Child`]: process::Child
148pub trait ChildExt: Sealed {
149 /// Obtains a reference to the [`PidFd`] created for this [`Child`], if available.
150 ///
151 /// A pidfd will only be available if its creation was requested with
152 /// [`create_pidfd`] when the corresponding [`Command`] was created.
153 ///
154 /// Even if requested, a pidfd may not be available due to an older
155 /// version of Linux being in use, or if some other error occurred.
156 ///
157 /// [`Command`]: process::Command
158 /// [`create_pidfd`]: CommandExt::create_pidfd
159 /// [`Child`]: process::Child
160 fn pidfd(&self) -> Result<&PidFd>;
161
162 /// Returns the [`PidFd`] created for this [`Child`], if available.
163 /// Otherwise self is returned.
164 ///
165 /// A pidfd will only be available if its creation was requested with
166 /// [`create_pidfd`] when the corresponding [`Command`] was created.
167 ///
168 /// Taking ownership of the PidFd consumes the Child to avoid pid reuse
169 /// races. Use [`pidfd`] and [`BorrowedFd::try_clone_to_owned`] if
170 /// you don't want to disassemble the Child yet.
171 ///
172 /// Even if requested, a pidfd may not be available due to an older
173 /// version of Linux being in use, or if some other error occurred.
174 ///
175 /// [`Command`]: process::Command
176 /// [`create_pidfd`]: CommandExt::create_pidfd
177 /// [`pidfd`]: ChildExt::pidfd
178 /// [`Child`]: process::Child
179 fn into_pidfd(self) -> crate::result::Result<PidFd, Self>
180 where
181 Self: Sized;
182}
183
184/// Os-specific extensions for [`Command`]
185///
186/// [`Command`]: process::Command
187pub trait CommandExt: Sealed {
188 /// Sets whether a [`PidFd`](struct@PidFd) should be created for the [`Child`]
189 /// spawned by this [`Command`].
190 /// By default, no pidfd will be created.
191 ///
192 /// The pidfd can be retrieved from the child with [`pidfd`] or [`into_pidfd`].
193 ///
194 /// A pidfd will only be created if it is possible to do so
195 /// in a guaranteed race-free manner. Otherwise, [`pidfd`] will return an error.
196 ///
197 /// If a pidfd has been successfully created and not been taken from the `Child`
198 /// then calls to `kill()`, `wait()` and `try_wait()` will use the pidfd
199 /// instead of the pid. This can prevent pid recycling races, e.g.
200 /// those caused by rogue libraries in the same process prematurely reaping
201 /// zombie children via `waitpid(-1, ...)` calls.
202 ///
203 /// [`Command`]: process::Command
204 /// [`Child`]: process::Child
205 /// [`pidfd`]: fn@ChildExt::pidfd
206 /// [`into_pidfd`]: ChildExt::into_pidfd
207 fn create_pidfd(&mut self, val: bool) -> &mut process::Command;
208}
209
210impl CommandExt for process::Command {
211 fn create_pidfd(&mut self, val: bool) -> &mut process::Command {
212 self.as_inner_mut().create_pidfd(val);
213 self
214 }
215}
216