linux-kernel - Re: [PATCH] rust: Add support for feeding entropy to randomness pool

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Message-ID:
 <JH0PR01MB551469C82704BD748841CC52ECAFA@JH0PR01MB5514.apcprd01.prod.exchangelabs.com>
Date: Sat, 13 Dec 2025 14:36:54 +0800
From: Weikang Guo <guoweikang.kernel@...look.com>
To: Matthew Maurer <mmaurer@...gle.com>, Miguel Ojeda <ojeda@...nel.org>
Cc: Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, "
 Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin
 <lossin@...nel.org>, Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl
 <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich
 <dakr@...nel.org>, linux-kernel@...r.kernel.org,
 rust-for-linux@...r.kernel.org
Subject: Re: [PATCH] rust: Add support for feeding entropy to randomness
 pool

On Fri, 12 Dec 2025 23:19:07 +0000
Matthew Maurer <mmaurer@...gle.com> wrote:

Hi, Matthew.

I think exposing add_device_randomness() in rust/kernel makes sense,
especially for Rust device drivers that already have access to
hardware-specific noise sources.

> Adds just enough support to allow device drivers to feed entropy to
> the central pool.
> 
> Signed-off-by: Matthew Maurer <mmaurer@...gle.com>
> ---
>  rust/kernel/lib.rs  |  1 +
>  rust/kernel/rand.rs | 14 ++++++++++++++
>  2 files changed, 15 insertions(+)
> 
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index
> f812cf12004286962985a068665443dc22c389a2..f93886ef4eec9c4356799f4b55916bc12c10c621
> 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs
> @@ -128,6 +128,7 @@
>  pub mod print;
>  pub mod processor;
>  pub mod ptr;
> +pub mod rand;
>  #[cfg(CONFIG_RUST_PWM_ABSTRACTIONS)]
>  pub mod pwm;
>  pub mod rbtree;
> diff --git a/rust/kernel/rand.rs b/rust/kernel/rand.rs
> new file mode 100644
> index
> 0000000000000000000000000000000000000000..b3fb30f40a8950ac7b47d48129eb89024a1cbd26
> --- /dev/null +++ b/rust/kernel/rand.rs
> @@ -0,0 +1,14 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +//! Randomness.
> +//!
> +//! C header:
> [`include/linux/random.h`](../../../../include/linux/random.h) +
> +use crate::bindings;
> +use crate::ffi::c_void;
> +
> +/// Adds the given buffer to the entropy pool.
I wonder if it would be useful to document more explicitly that this
function does not credit entropy, matching the C-side semantics, to
avoid semantic misuse by drivers.
> +pub fn add_device_randomness(buf: &[u8]) {
> +    // SAFETY: We just need the pointer to be valid for the length,
> which a slice provides.
>From a Rust safety-contract perspective, this wrapper looks fine to be
safe, since the pointer is not retained and the data is only read
synchronously.(may be you )
> +    unsafe {
> bindings::add_device_randomness(buf.as_ptr().cast::<c_void>(),
> buf.len()) }; +}
> 
> ---
> base-commit: 008d3547aae5bc86fac3eda317489169c3fda112
> change-id: 20251029-add-entropy-f57e12ebe110
> 
> Best regards,