kernel/
pid_namespace.rs

1// SPDX-License-Identifier: GPL-2.0
2
3// Copyright (c) 2024 Christian Brauner <brauner@kernel.org>
4
5//! Pid namespaces.
6//!
7//! C header: [`include/linux/pid_namespace.h`](srctree/include/linux/pid_namespace.h) and
8//! [`include/linux/pid.h`](srctree/include/linux/pid.h)
9
10use crate::{bindings, sync::aref::AlwaysRefCounted, types::Opaque};
11use core::ptr;
12use safety_macro::safety;
13/// Wraps the kernel's `struct pid_namespace`. Thread safe.
14///
15/// This structure represents the Rust abstraction for a C `struct pid_namespace`. This
16/// implementation abstracts the usage of an already existing C `struct pid_namespace` within Rust
17/// code that we get passed from the C side.
18#[repr(transparent)]
19pub struct PidNamespace {
20    inner: Opaque<bindings::pid_namespace>,
21}
22
23impl PidNamespace {
24    /// Returns a raw pointer to the inner C struct.
25    #[inline]
26    pub fn as_ptr(&self) -> *mut bindings::pid_namespace {
27        self.inner.get()
28    }
29
30    /// Creates a reference to a [`PidNamespace`] from a valid pointer.
31    ///
32    /// # Safety
33    ///
34    /// The caller must ensure that `ptr` is valid and remains valid for the lifetime of the
35    /// returned [`PidNamespace`] reference.
36    #[safety{ValidPtr(ptr, bindings::pid_namespace, 1)}]
37    pub unsafe fn from_ptr<'a>(ptr: *const bindings::pid_namespace) -> &'a Self {
38        // SAFETY: The safety requirements guarantee the validity of the dereference, while the
39        // `PidNamespace` type being transparent makes the cast ok.
40        unsafe { &*ptr.cast() }
41    }
42}
43
44// SAFETY: Instances of `PidNamespace` are always reference-counted.
45unsafe impl AlwaysRefCounted for PidNamespace {
46    #[inline]
47    fn inc_ref(&self) {
48        // SAFETY: The existence of a shared reference means that the refcount is nonzero.
49        unsafe { bindings::get_pid_ns(self.as_ptr()) };
50    }
51
52    #[inline]
53    unsafe fn dec_ref(obj: ptr::NonNull<PidNamespace>) {
54        // SAFETY: The safety requirements guarantee that the refcount is non-zero.
55        unsafe { bindings::put_pid_ns(obj.cast().as_ptr()) }
56    }
57}
58
59// SAFETY:
60// - `PidNamespace::dec_ref` can be called from any thread.
61// - It is okay to send ownership of `PidNamespace` across thread boundaries.
62unsafe impl Send for PidNamespace {}
63
64// SAFETY: It's OK to access `PidNamespace` through shared references from other threads because
65// we're either accessing properties that don't change or that are properly synchronised by C code.
66unsafe impl Sync for PidNamespace {}
kernel/pid_namespace.rs

kernel/
pid_namespace.rs
