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Message-ID: <QDJDJxiCJaB6_91GlTTIJmyfDegTJpRXwrcPRPubdau5diJRPA96rLxC1oILb0zKKDCQ9703xQn4diE7TCtRpknvg-9yAXoigoKoXwxj9fQ=@protonmail.com>
Date: Sat, 24 Jun 2023 14:55:03 +0000
From: Björn Roy Baron <bjorn3_gh@...tonmail.com>
To: Benno Lossin <benno.lossin@...ton.me>
Cc: Miguel Ojeda <ojeda@...nel.org>,
Wedson Almeida Filho <wedsonaf@...il.com>,
Alex Gaynor <alex.gaynor@...il.com>,
Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
Alice Ryhl <aliceryhl@...gle.com>,
Andreas Hindborg <nmi@...aspace.dk>,
rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
patches@...ts.linux.dev, Asahi Lina <lina@...hilina.net>
Subject: Re: [PATCH 2/7] rust: add derive macro for `Zeroable`
On Saturday, June 24th, 2023 at 11:25, Benno Lossin <benno.lossin@...ton.me> wrote:
> Add a derive proc-macro for the `Zeroable` trait. The macro supports
> structs where every field implements the `Zeroable` trait. This way
> `unsafe` implementations can be avoided.
>
> The macro is split into two parts:
> - a proc-macro to parse generics into impl and ty generics,
> - a declarative macro that expands to the impl block.
>
> Suggested-by: Asahi Lina <lina@...hilina.net>
> Signed-off-by: Benno Lossin <benno.lossin@...ton.me>
Reviewed-by: Björn Roy Baron <bjorn3_gh@...tonmail.com>
> ---
> rust/kernel/init/macros.rs | 28 ++++++++++++++++++++++++++++
> rust/kernel/prelude.rs | 2 +-
> rust/macros/lib.rs | 20 ++++++++++++++++++++
> rust/macros/quote.rs | 6 ++++++
> rust/macros/zeroable.rs | 25 +++++++++++++++++++++++++
> 5 files changed, 80 insertions(+), 1 deletion(-)
> create mode 100644 rust/macros/zeroable.rs
>
> diff --git a/rust/kernel/init/macros.rs b/rust/kernel/init/macros.rs
> index fbaebd34f218..e8165ff53a94 100644
> --- a/rust/kernel/init/macros.rs
> +++ b/rust/kernel/init/macros.rs
> @@ -1213,3 +1213,31 @@ macro_rules! __init_internal {
> );
> };
> }
> +
> +#[doc(hidden)]
> +#[macro_export]
> +macro_rules! __derive_zeroable {
> + (parse_input:
> + @sig(
> + $(#[$($struct_attr:tt)*])*
> + $vis:vis struct $name:ident
> + $(where $($whr:tt)*)?
> + ),
> + @impl_generics($($impl_generics:tt)*),
> + @ty_generics($($ty_generics:tt)*),
> + @body({
> + $(
> + $(#[$($field_attr:tt)*])*
> + $field:ident : $field_ty:ty
> + ),* $(,)?
> + }),
> + ) => {
> + // SAFETY: every field type implements `Zeroable` and padding bytes may be zero.
> + #[automatically_derived]
> + unsafe impl<$($impl_generics)*> $crate::Zeroable for $name<$($ty_generics)*>
> + where
> + $($field_ty: $crate::Zeroable,)*
> + $($($whr)*)?
> + {}
> + };
> +}
> diff --git a/rust/kernel/prelude.rs b/rust/kernel/prelude.rs
> index c28587d68ebc..ae21600970b3 100644
> --- a/rust/kernel/prelude.rs
> +++ b/rust/kernel/prelude.rs
> @@ -18,7 +18,7 @@
> pub use alloc::{boxed::Box, vec::Vec};
>
> #[doc(no_inline)]
> -pub use macros::{module, pin_data, pinned_drop, vtable};
> +pub use macros::{module, pin_data, pinned_drop, vtable, Zeroable};
>
> pub use super::build_assert;
>
> diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
> index 3fc74cb4ea19..9f056a5c780a 100644
> --- a/rust/macros/lib.rs
> +++ b/rust/macros/lib.rs
> @@ -10,6 +10,7 @@
> mod pin_data;
> mod pinned_drop;
> mod vtable;
> +mod zeroable;
>
> use proc_macro::TokenStream;
>
> @@ -246,3 +247,22 @@ pub fn pin_data(inner: TokenStream, item: TokenStream) -> TokenStream {
> pub fn pinned_drop(args: TokenStream, input: TokenStream) -> TokenStream {
> pinned_drop::pinned_drop(args, input)
> }
> +
> +/// Derives the [`Zeroable`] trait for the given struct.
> +///
> +/// This can only be used for structs where every field implements the [`Zeroable`] trait.
> +///
> +/// # Examples
> +///
> +/// ```rust
> +/// #[derive(Zeroable)]
> +/// pub struct DriverData {
> +/// id: i64,
> +/// buf_ptr: *mut u8,
> +/// len: usize,
> +/// }
> +/// ```
> +#[proc_macro_derive(Zeroable)]
> +pub fn derive_zeroable(input: TokenStream) -> TokenStream {
> + zeroable::derive(input)
> +}
> diff --git a/rust/macros/quote.rs b/rust/macros/quote.rs
> index dddbb4e6f4cb..b76c198a4ed5 100644
> --- a/rust/macros/quote.rs
> +++ b/rust/macros/quote.rs
> @@ -124,6 +124,12 @@ macro_rules! quote_spanned {
> ));
> quote_spanned!(@proc $v $span $($tt)*);
> };
> + (@proc $v:ident $span:ident ; $($tt:tt)*) => {
> + $v.push(::proc_macro::TokenTree::Punct(
> + ::proc_macro::Punct::new(';', ::proc_macro::Spacing::Alone)
> + ));
> + quote_spanned!(@proc $v $span $($tt)*);
> + };
> (@proc $v:ident $span:ident $id:ident $($tt:tt)*) => {
> $v.push(::proc_macro::TokenTree::Ident(::proc_macro::Ident::new(stringify!($id), $span)));
> quote_spanned!(@proc $v $span $($tt)*);
> diff --git a/rust/macros/zeroable.rs b/rust/macros/zeroable.rs
> new file mode 100644
> index 000000000000..cddb866c44ef
> --- /dev/null
> +++ b/rust/macros/zeroable.rs
> @@ -0,0 +1,25 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +use crate::helpers::{parse_generics, Generics};
> +use proc_macro::TokenStream;
> +
> +pub(crate) fn derive(input: TokenStream) -> TokenStream {
> + let (
> + Generics {
> + impl_generics,
> + ty_generics,
> + },
> + mut rest,
> + ) = parse_generics(input);
> + // This should be the body of the struct `{...}`.
> + let last = rest.pop();
> + quote! {
> + ::kernel::__derive_zeroable!(
> + parse_input:
> + @sig(#(#rest)*),
> + @impl_generics(#(#impl_generics)*),
> + @ty_generics(#(#ty_generics)*),
> + @body(#last),
> + );
> + }
> +}
> --
> 2.41.0
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