69 lines
2.4 KiB
Rust
69 lines
2.4 KiB
Rust
// SPDX-License-Identifier: GPL-2.0
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// Copyright (c) 2024 Christian Brauner <brauner@kernel.org>
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//! Pid namespaces.
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//!
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//! C header: [`include/linux/pid_namespace.h`](srctree/include/linux/pid_namespace.h) and
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//! [`include/linux/pid.h`](srctree/include/linux/pid.h)
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use crate::{
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bindings,
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types::{AlwaysRefCounted, Opaque},
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};
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use core::ptr;
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/// Wraps the kernel's `struct pid_namespace`. Thread safe.
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///
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/// This structure represents the Rust abstraction for a C `struct pid_namespace`. This
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/// implementation abstracts the usage of an already existing C `struct pid_namespace` within Rust
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/// code that we get passed from the C side.
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#[repr(transparent)]
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pub struct PidNamespace {
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inner: Opaque<bindings::pid_namespace>,
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}
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impl PidNamespace {
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/// Returns a raw pointer to the inner C struct.
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#[inline]
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pub fn as_ptr(&self) -> *mut bindings::pid_namespace {
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self.inner.get()
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}
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/// Creates a reference to a [`PidNamespace`] from a valid pointer.
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///
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/// # Safety
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///
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/// The caller must ensure that `ptr` is valid and remains valid for the lifetime of the
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/// returned [`PidNamespace`] reference.
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pub unsafe fn from_ptr<'a>(ptr: *const bindings::pid_namespace) -> &'a Self {
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// SAFETY: The safety requirements guarantee the validity of the dereference, while the
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// `PidNamespace` type being transparent makes the cast ok.
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unsafe { &*ptr.cast() }
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}
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}
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// SAFETY: Instances of `PidNamespace` are always reference-counted.
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unsafe impl AlwaysRefCounted for PidNamespace {
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#[inline]
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fn inc_ref(&self) {
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// SAFETY: The existence of a shared reference means that the refcount is nonzero.
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unsafe { bindings::get_pid_ns(self.as_ptr()) };
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}
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#[inline]
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unsafe fn dec_ref(obj: ptr::NonNull<PidNamespace>) {
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// SAFETY: The safety requirements guarantee that the refcount is non-zero.
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unsafe { bindings::put_pid_ns(obj.cast().as_ptr()) }
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}
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}
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// SAFETY:
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// - `PidNamespace::dec_ref` can be called from any thread.
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// - It is okay to send ownership of `PidNamespace` across thread boundaries.
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unsafe impl Send for PidNamespace {}
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// SAFETY: It's OK to access `PidNamespace` through shared references from other threads because
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// we're either accessing properties that don't change or that are properly synchronised by C code.
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unsafe impl Sync for PidNamespace {}
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