[PATCH V8 05/14] rust: Add bindings for cpumask

Viresh Kumar
2025-02-06T09:29:13Z

This patch adds basic Rust bindings for struct cpumask.

These will be used by Rust based cpufreq / OPP core.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
MAINTAINERS | 1 +
rust/kernel/cpumask.rs | 138 +++++++++++++++++++++++++++++++++++++++++
rust/kernel/lib.rs | 1 +
3 files changed, 140 insertions(+)
create mode 100644 rust/kernel/cpumask.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index bfc1bf2ebd77..ff4511914e0a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4022,6 +4022,7 @@ F: lib/find_bit.c
F: lib/find_bit_benchmark.c
F: lib/test_bitmap.c
F: rust/helpers/cpumask.c
+F: rust/kernel/cpumask.rs
F: tools/include/linux/bitfield.h
F: tools/include/linux/bitmap.h
F: tools/include/linux/bits.h
diff --git a/rust/kernel/cpumask.rs b/rust/kernel/cpumask.rs
new file mode 100644
index 000000000000..b0be8c75a2c2
--- /dev/null
+++ b/rust/kernel/cpumask.rs
@@ -0,0 +1,138 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! CPU mask abstractions.
+//!
+//! C header: [`include/linux/cpumask.h`](srctree/include/linux/cpumask.h)
+
+use crate::{bindings, error::Result, prelude::ENOMEM};
+
+#[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
+use crate::prelude::{KBox, GFP_KERNEL};
+
+#[cfg(CONFIG_CPUMASK_OFFSTACK)]
+use core::ptr;
+
+/// A simple implementation of `struct cpumask` from the C code.
+pub struct Cpumask {
+ ptr: *mut bindings::cpumask,
+ owned: bool,
+}
+
+impl Cpumask {
+ /// Creates empty cpumask.
+ #[cfg(CONFIG_CPUMASK_OFFSTACK)]
+ pub fn new() -> Result<Self> {
+ let mut ptr: *mut bindings::cpumask = ptr::null_mut();
+
+ // SAFETY: Depending on the value of `gfp_flags`, this call may sleep. Other than that, it
+ // is always safe to call this method.
+ if !unsafe { bindings::zalloc_cpumask_var(&mut ptr, bindings::GFP_KERNEL) } {
+ return Err(ENOMEM);
+ }
+
+ Ok(Self { ptr, owned: true })
+ }
+
+ /// Creates empty cpumask.
+ #[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
+ pub fn new() -> Result<Self> {
+ let ptr = KBox::into_raw(KBox::new([bindings::cpumask::default(); 1], GFP_KERNEL)?);
+
+ // SAFETY: Depending on the value of `gfp_flags`, this call may sleep. Other than that, it
+ // is always safe to call this method.
+ if !unsafe { bindings::zalloc_cpumask_var(ptr, bindings::GFP_KERNEL) } {
+ return Err(ENOMEM);
+ }
+
+ Ok(Self {
+ ptr: ptr as *mut _,
+ owned: true,
+ })
+ }
+
+ /// Creates a new abstraction instance of an existing `struct cpumask` pointer.
+ ///
+ /// # Safety
+ ///
+ /// Callers must ensure that `ptr` is valid, and non-null.
+ #[cfg(CONFIG_CPUMASK_OFFSTACK)]
+ pub unsafe fn get_cpumask(ptr: &mut *mut bindings::cpumask) -> Self {
+ Self {
+ ptr: *ptr,
+ owned: false,
+ }
+ }
+
+ /// Creates a new abstraction instance of an existing `struct cpumask` pointer.
+ ///
+ /// # Safety
+ ///
+ /// Callers must ensure that `ptr` is valid, and non-null.
+ #[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
+ pub unsafe fn get_cpumask(ptr: &mut bindings::cpumask_var_t) -> Self {
+ Self {
+ ptr: ptr as *mut _,
+ owned: false,
+ }
+ }
+
+ /// Obtain the raw `struct cpumask *`.
+ pub fn as_raw(&mut self) -> *mut bindings::cpumask {
+ self.ptr
+ }
+
+ /// Sets CPU in the cpumask.
+ ///
+ /// Update the cpumask with a single CPU.
+ pub fn set(&mut self, cpu: u32) {
+ // SAFETY: `ptr` is guaranteed to be valid for the lifetime of `self`. And it is safe to
+ // call `cpumask_set_cpus()` for any CPU.
+ unsafe { bindings::cpumask_set_cpu(cpu, self.ptr) };
+ }
+
+ /// Clears CPU in the cpumask.
+ ///
+ /// Update the cpumask with a single CPU.
+ pub fn clear(&mut self, cpu: i32) {
+ // SAFETY: `ptr` is guaranteed to be valid for the lifetime of `self`. And it is safe to
+ // call `cpumask_clear_cpu()` for any CPU.
+ unsafe { bindings::cpumask_clear_cpu(cpu, self.ptr) };
+ }
+
+ /// Sets all CPUs in the cpumask.
+ pub fn set_all(&mut self) {
+ // SAFETY: `ptr` is guaranteed to be valid for the lifetime of `self`. And it is safe to
+ // call `cpumask_setall()`.
+ unsafe { bindings::cpumask_setall(self.ptr) };
+ }
+
+ /// Gets weight of a cpumask.
+ pub fn weight(&self) -> u32 {
+ // SAFETY: `ptr` is guaranteed to be valid for the lifetime of `self`. And it is safe to
+ // call `cpumask_weight()`.
+ unsafe { bindings::cpumask_weight(self.ptr) }
+ }
+
+ /// Copies cpumask.
+ pub fn copy(&self, dstp: &mut Self) {
+ // SAFETY: `ptr` is guaranteed to be valid for the lifetime of `self`. And it is safe to
+ // call `cpumask_copy()`.
+ unsafe { bindings::cpumask_copy(dstp.as_raw(), self.ptr) };
+ }
+}
+
+impl Drop for Cpumask {
+ fn drop(&mut self) {
+ if self.owned {
+ // SAFETY: `ptr` is guaranteed to be valid for the lifetime of `self`. And it is safe
+ // to call `free_cpumask_var()`.
+ unsafe { bindings::free_cpumask_var(self.ptr) }
+
+ #[cfg(not(CONFIG_CPUMASK_OFFSTACK))]
+ // SAFETY: The pointer was earlier initialized from the result of `KBox::into_raw()`.
+ unsafe {
+ drop(KBox::from_raw(self.ptr))
+ };
+ }
+ }
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 415c500212dd..ccbf7fa087a0 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -41,6 +41,7 @@
#[doc(hidden)]
pub mod build_assert;
pub mod cpu;
+pub mod cpumask;
pub mod cred;
pub mod device;
pub mod device_id;
--
2.31.1.272.g89b43f80a514