[PATCH] rust: Add support for feeding entropy to randomness pool

[PATCH] rust: Add support for feeding entropy to randomness pool

[Matthew Maurer]

Adds just enough support to allow device drivers to feed entropy to the
central pool.

Signed-off-by: Matthew Maurer <mmaurer@google.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.
+pub fn add_device_randomness(buf: &[u8]) {
+    // SAFETY: We just need the pointer to be valid for the length, which a slice provides.
+    unsafe { bindings::add_device_randomness(buf.as_ptr().cast::<c_void>(), buf.len()) };
+}

---
base-commit: 008d3547aae5bc86fac3eda317489169c3fda112
change-id: 20251029-add-entropy-f57e12ebe110

Best regards,
-- 
Matthew Maurer <mmaurer@google.com>

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

[Matthew Maurer]

On Fri, Dec 12, 2025 at 3:19 PM Matthew Maurer <mmaurer@google.com> wrote:
>
> Adds just enough support to allow device drivers to feed entropy to the
> central pool.
>
> Signed-off-by: Matthew Maurer <mmaurer@google.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;

I've just noticed that the rebase misalphabetized this. I'll send up a
v2 after folks make any comments they want, but figure I don't need to
spam you for now.

>  #[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.
> +pub fn add_device_randomness(buf: &[u8]) {
> +    // SAFETY: We just need the pointer to be valid for the length, which a slice provides.
> +    unsafe { bindings::add_device_randomness(buf.as_ptr().cast::<c_void>(), buf.len()) };
> +}
>
> ---
> base-commit: 008d3547aae5bc86fac3eda317489169c3fda112
> change-id: 20251029-add-entropy-f57e12ebe110
>
> Best regards,
> --
> Matthew Maurer <mmaurer@google.com>
>

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

[Weikang Guo]

On Fri, 12 Dec 2025 23:19:07 +0000
Matthew Maurer <mmaurer@google.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@google.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,