1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165

//! Linux-specific extensions to primitives in the [`std::process`] module.
//!
//! [`std::process`]: crate::process

#![unstable(feature = "linux_pidfd", issue = "82971")]

use crate::io::Result;
use crate::os::unix::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, OwnedFd, RawFd};
use crate::process;
use crate::sealed::Sealed;
#[cfg(not(doc))]
use crate::sys::fd::FileDesc;
use crate::sys_common::{AsInner, AsInnerMut, FromInner, IntoInner};

#[cfg(doc)]
struct FileDesc;

/// This type represents a file descriptor that refers to a process.
///
/// A `PidFd` can be obtained by setting the corresponding option on [`Command`]
/// with [`create_pidfd`]. Subsequently, the created pidfd can be retrieved
/// from the [`Child`] by calling [`pidfd`] or [`take_pidfd`].
///
/// Example:
/// ```no_run
/// #![feature(linux_pidfd)]
/// use std::os::linux::process::{CommandExt, ChildExt};
/// use std::process::Command;
///
/// let mut child = Command::new("echo")
///     .create_pidfd(true)
///     .spawn()
///     .expect("Failed to spawn child");
///
/// let pidfd = child
///     .take_pidfd()
///     .expect("Failed to retrieve pidfd");
///
/// // The file descriptor will be closed when `pidfd` is dropped.
/// ```
/// Refer to the man page of [`pidfd_open(2)`] for further details.
///
/// [`Command`]: process::Command
/// [`create_pidfd`]: CommandExt::create_pidfd
/// [`Child`]: process::Child
/// [`pidfd`]: fn@ChildExt::pidfd
/// [`take_pidfd`]: ChildExt::take_pidfd
/// [`pidfd_open(2)`]: https://man7.org/linux/man-pages/man2/pidfd_open.2.html
#[derive(Debug)]
pub struct PidFd {
    inner: FileDesc,
}

impl AsInner<FileDesc> for PidFd {
    fn as_inner(&self) -> &FileDesc {
        &self.inner
    }
}

impl FromInner<FileDesc> for PidFd {
    fn from_inner(inner: FileDesc) -> PidFd {
        PidFd { inner }
    }
}

impl IntoInner<FileDesc> for PidFd {
    fn into_inner(self) -> FileDesc {
        self.inner
    }
}

impl AsRawFd for PidFd {
    fn as_raw_fd(&self) -> RawFd {
        self.as_inner().as_raw_fd()
    }
}

impl FromRawFd for PidFd {
    unsafe fn from_raw_fd(fd: RawFd) -> Self {
        Self::from_inner(FileDesc::from_raw_fd(fd))
    }
}

impl IntoRawFd for PidFd {
    fn into_raw_fd(self) -> RawFd {
        self.into_inner().into_raw_fd()
    }
}

impl AsFd for PidFd {
    fn as_fd(&self) -> BorrowedFd<'_> {
        self.as_inner().as_fd()
    }
}

impl From<OwnedFd> for PidFd {
    fn from(fd: OwnedFd) -> Self {
        Self::from_inner(FileDesc::from_inner(fd))
    }
}

impl From<PidFd> for OwnedFd {
    fn from(pid_fd: PidFd) -> Self {
        pid_fd.into_inner().into_inner()
    }
}

/// Os-specific extensions for [`Child`]
///
/// [`Child`]: process::Child
pub trait ChildExt: Sealed {
    /// Obtains a reference to the [`PidFd`] created for this [`Child`], if available.
    ///
    /// A pidfd will only be available if its creation was requested with
    /// [`create_pidfd`] when the corresponding [`Command`] was created.
    ///
    /// Even if requested, a pidfd may not be available due to an older
    /// version of Linux being in use, or if some other error occurred.
    ///
    /// [`Command`]: process::Command
    /// [`create_pidfd`]: CommandExt::create_pidfd
    /// [`Child`]: process::Child
    fn pidfd(&self) -> Result<&PidFd>;

    /// Takes ownership of the [`PidFd`] created for this [`Child`], if available.
    ///
    /// A pidfd will only be available if its creation was requested with
    /// [`create_pidfd`] when the corresponding [`Command`] was created.
    ///
    /// Even if requested, a pidfd may not be available due to an older
    /// version of Linux being in use, or if some other error occurred.
    ///
    /// [`Command`]: process::Command
    /// [`create_pidfd`]: CommandExt::create_pidfd
    /// [`Child`]: process::Child
    fn take_pidfd(&mut self) -> Result<PidFd>;
}

/// Os-specific extensions for [`Command`]
///
/// [`Command`]: process::Command
pub trait CommandExt: Sealed {
    /// Sets whether a [`PidFd`](struct@PidFd) should be created for the [`Child`]
    /// spawned by this [`Command`].
    /// By default, no pidfd will be created.
    ///
    /// The pidfd can be retrieved from the child with [`pidfd`] or [`take_pidfd`].
    ///
    /// A pidfd will only be created if it is possible to do so
    /// in a guaranteed race-free manner (e.g. if the `clone3` system call
    /// is supported). Otherwise, [`pidfd`] will return an error.
    ///
    /// [`Command`]: process::Command
    /// [`Child`]: process::Child
    /// [`pidfd`]: fn@ChildExt::pidfd
    /// [`take_pidfd`]: ChildExt::take_pidfd
    fn create_pidfd(&mut self, val: bool) -> &mut process::Command;
}

impl CommandExt for process::Command {
    fn create_pidfd(&mut self, val: bool) -> &mut process::Command {
        self.as_inner_mut().create_pidfd(val);
        self
    }
}