linux-kernel - [PATCH V8 03/14] rust: cpu: Add from

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <35ef3767cb9e65cb4c95df7ed50c6f3f6190066e.1738832118.git.viresh.kumar@linaro.org>
Date: Thu,  6 Feb 2025 14:58:24 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
	Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
	Danilo Krummrich <dakr@...hat.com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Trevor Gross <tmgross@...ch.edu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>
Cc: Viresh Kumar <viresh.kumar@...aro.org>,
	linux-pm@...r.kernel.org,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Stephen Boyd <sboyd@...nel.org>,
	Nishanth Menon <nm@...com>,
	rust-for-linux@...r.kernel.org,
	Manos Pitsidianakis <manos.pitsidianakis@...aro.org>,
	Erik Schilling <erik.schilling@...aro.org>,
	Alex Bennée <alex.bennee@...aro.org>,
	Joakim Bech <joakim.bech@...aro.org>,
	Rob Herring <robh@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH V8 03/14] rust: cpu: Add from_cpu()

This implements cpu::from_cpu(), which returns a reference to
Device for a CPU. The C struct is created at initialization time for
CPUs and is never freed and so ARef isn't returned from this function.

The new helper will be used by Rust based cpufreq drivers.

Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 MAINTAINERS                     |  1 +
 rust/bindings/bindings_helper.h |  1 +
 rust/kernel/cpu.rs              | 31 +++++++++++++++++++++++++++++++
 rust/kernel/lib.rs              |  1 +
 4 files changed, 34 insertions(+)
 create mode 100644 rust/kernel/cpu.rs

diff --git a/MAINTAINERS b/MAINTAINERS
index 896a307fa065..ee6709599df5 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6034,6 +6034,7 @@ F:	include/linux/cpuhotplug.h
 F:	include/linux/smpboot.h
 F:	kernel/cpu.c
 F:	kernel/smpboot.*
+F:	rust/kernel/cpu.rs
 
 CPU IDLE TIME MANAGEMENT FRAMEWORK
 M:	"Rafael J. Wysocki" <rafael@...nel.org>
diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index 55354e4dec14..fda1e0d8f376 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -10,6 +10,7 @@
 #include <linux/blk-mq.h>
 #include <linux/blk_types.h>
 #include <linux/blkdev.h>
+#include <linux/cpu.h>
 #include <linux/cred.h>
 #include <linux/errname.h>
 #include <linux/ethtool.h>
diff --git a/rust/kernel/cpu.rs b/rust/kernel/cpu.rs
new file mode 100644
index 000000000000..3054165d3818
--- /dev/null
+++ b/rust/kernel/cpu.rs
@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Generic CPU definitions.
+//!
+//! C header: [`include/linux/cpu.h`](srctree/include/linux/cpu.h)
+
+use crate::{bindings, device::Device, error::Result, prelude::ENODEV};
+
+/// Creates a new instance of CPU's device.
+///
+/// # Safety
+///
+/// Reference counting is not implemented for the CPU device in the C code. When a CPU is
+/// hot-unplugged, the corresponding CPU device is unregistered, but its associated memory
+/// is not freed.
+///
+/// Callers must ensure that the CPU device is not used after it has been unregistered.
+/// This can be achieved, for example, by registering a CPU hotplug notifier and removing
+/// any references to the CPU device within the notifier's callback.
+pub unsafe fn from_cpu(cpu: u32) -> Result<&'static Device> {
+    // SAFETY: The pointer returned by `get_cpu_device()`, if not `NULL`, is a valid pointer to
+    // a `struct device` and is never freed by the C code.
+    let ptr = unsafe { bindings::get_cpu_device(cpu) };
+    if ptr.is_null() {
+        return Err(ENODEV);
+    }
+
+    // SAFETY: The pointer returned by `get_cpu_device()`, if not `NULL`, is a valid pointer to
+    // a `struct device` and is never freed by the C code.
+    Ok(unsafe { Device::as_ref(ptr) })
+}
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 496ed32b0911..415c500212dd 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -40,6 +40,7 @@
 pub mod block;
 #[doc(hidden)]
 pub mod build_assert;
+pub mod cpu;
 pub mod cred;
 pub mod device;
 pub mod device_id;
-- 
2.31.1.272.g89b43f80a514