linux-kernel - Re: [PATCH v4 05/28] rust: alloc: add module `allocator

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Message-ID: <7f4b91e6-aae8-4e17-9fcd-4b1d0b2de9a0@proton.me>
Date: Tue, 06 Aug 2024 16:54:10 +0000
From: Benno Lossin <benno.lossin@...ton.me>
To: Danilo Krummrich <dakr@...nel.org>, ojeda@...nel.org, alex.gaynor@...il.com, wedsonaf@...il.com, boqun.feng@...il.com, gary@...yguo.net, bjorn3_gh@...tonmail.com, a.hindborg@...sung.com, aliceryhl@...gle.com, akpm@...ux-foundation.org
Cc: daniel.almeida@...labora.com, faith.ekstrand@...labora.com, boris.brezillon@...labora.com, lina@...hilina.net, mcanal@...lia.com, zhiw@...dia.com, acurrid@...dia.com, cjia@...dia.com, jhubbard@...dia.com, airlied@...hat.com, ajanulgu@...hat.com, lyude@...hat.com, linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v4 05/28] rust: alloc: add module `allocator_test`

On 05.08.24 17:19, Danilo Krummrich wrote:
> `Allocator`s, such as `Kmalloc`, will be used by e.g. `Box` and `Vec` in
> subsequent patches, and hence this dependency propagates throughout the
> whole kernel.
> 
> Add the `allocator_test` module that provides an empty implementation
> for all `Allocator`s in the kernel, such that we don't break the
> `rusttest` make target in subsequent patches.

This is confusing, since you are talking about both our new `Allocator`
trait, allocators and the `alloc` crate `Allocator`.

> Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>
> Signed-off-by: Danilo Krummrich <dakr@...nel.org>
> ---
>  rust/kernel/alloc.rs                |  9 +++++++--
>  rust/kernel/alloc/allocator_test.rs | 19 +++++++++++++++++++
>  2 files changed, 26 insertions(+), 2 deletions(-)
>  create mode 100644 rust/kernel/alloc/allocator_test.rs
> 
> diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs
> index bc01a17df5e0..942e2755f217 100644
> --- a/rust/kernel/alloc.rs
> +++ b/rust/kernel/alloc.rs
> @@ -2,12 +2,17 @@
> 
>  //! Extensions to the [`alloc`] crate.
> 
> -#[cfg(not(test))]
> -#[cfg(not(testlib))]
> +#[cfg(not(any(test, testlib)))]
>  pub mod allocator;
>  pub mod box_ext;
>  pub mod vec_ext;
> 
> +#[cfg(any(test, testlib))]
> +pub mod allocator_test;
> +
> +#[cfg(any(test, testlib))]
> +pub use self::allocator_test as allocator;
> +
>  /// Indicates an allocation error.
>  #[derive(Copy, Clone, PartialEq, Eq, Debug)]
>  pub struct AllocError;
> diff --git a/rust/kernel/alloc/allocator_test.rs b/rust/kernel/alloc/allocator_test.rs
> new file mode 100644
> index 000000000000..4785efc474a7
> --- /dev/null
> +++ b/rust/kernel/alloc/allocator_test.rs
> @@ -0,0 +1,19 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#![allow(missing_docs)]
> +
> +use super::{AllocError, Allocator, Flags};
> +use core::alloc::Layout;
> +use core::ptr::NonNull;
> +
> +pub struct Kmalloc;
> +
> +unsafe impl Allocator for Kmalloc {
> +    unsafe fn realloc(
> +        _ptr: Option<NonNull<u8>>,
> +        _layout: Layout,
> +        _flags: Flags,
> +    ) -> Result<NonNull<[u8]>, AllocError> {
> +        panic!();

Does `build_error!()` also work? If yes, then I would prefer that.

---
Cheers,
Benno

> +    }
> +}
> --
> 2.45.2
>