[PATCH 06/11] rust: macros: convert `#[export]` to use `syn`

Gary Guo
2025-12-11T19:29:54Z

From: Gary Guo <gary@garyguo.net>

This eliminates the custom `function_name` helper.

Signed-off-by: Gary Guo <gary@garyguo.net>
---
rust/macros/export.rs | 24 +++++++++---------------
rust/macros/helpers.rs | 18 ------------------
rust/macros/lib.rs | 5 +++--
3 files changed, 12 insertions(+), 35 deletions(-)

diff --git a/rust/macros/export.rs b/rust/macros/export.rs
index 92d9b30971929..6d53521f62fc7 100644
--- a/rust/macros/export.rs
+++ b/rust/macros/export.rs
@@ -3,19 +3,14 @@
use proc_macro2::TokenStream;
use quote::quote;

-use crate::helpers::function_name;
-
/// Please see [`crate::export`] for documentation.
-pub(crate) fn export(_attr: TokenStream, ts: TokenStream) -> TokenStream {
- let Some(name) = function_name(ts.clone()) else {
- return "::core::compile_error!(\"The #[export] attribute must be used on a function.\");"
- .parse::<TokenStream>()
- .unwrap();
- };
+pub(crate) fn export(f: syn::ItemFn) -> TokenStream {
+ let name = &f.sig.ident;

- // This verifies that the function has the same signature as the declaration generated by
- // bindgen. It makes use of the fact that all branches of an if/else must have the same type.
- let signature_check = quote!(
+ quote! {
+ // This verifies that the function has the same signature as the declaration generated by
+ // bindgen. It makes use of the fact that all branches of an if/else must have the same
+ // type.
const _: () = {
if true {
::kernel::bindings::#name
@@ -23,9 +18,8 @@ pub(crate) fn export(_attr: TokenStream, ts: TokenStream) -> TokenStream {
#name
};
};
- );
-
- let no_mangle = quote!(#[no_mangle]);

- TokenStream::from_iter([signature_check, no_mangle, ts])
+ #[no_mangle]
+ #f
+ }
}
diff --git a/rust/macros/helpers.rs b/rust/macros/helpers.rs
index f6bbdb02d9d7d..754c827cc21e1 100644
--- a/rust/macros/helpers.rs
+++ b/rust/macros/helpers.rs
@@ -2,7 +2,6 @@

use proc_macro2::{
token_stream,
- Ident,
TokenStream,
TokenTree, //
};
@@ -50,23 +49,6 @@ pub(crate) fn value(&self) -> String {
}
}

-/// Given a function declaration, finds the name of the function.
-pub(crate) fn function_name(input: TokenStream) -> Option<Ident> {
- let mut input = input.into_iter();
- while let Some(token) = input.next() {
- match token {
- TokenTree::Ident(i) if i.to_string() == "fn" => {
- if let Some(TokenTree::Ident(i)) = input.next() {
- return Some(i);
- }
- return None;
- }
- _ => continue,
- }
- }
- None
-}
-
pub(crate) fn file() -> String {
#[cfg(not(CONFIG_RUSTC_HAS_SPAN_FILE))]
{
diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs
index 4e440deaed853..870a42d41ac91 100644
--- a/rust/macros/lib.rs
+++ b/rust/macros/lib.rs
@@ -206,8 +206,9 @@ pub fn vtable(attr: TokenStream, input: TokenStream) -> TokenStream {
/// This macro is *not* the same as the C macros `EXPORT_SYMBOL_*`. All Rust symbols are currently
/// automatically exported with `EXPORT_SYMBOL_GPL`.
#[proc_macro_attribute]
-pub fn export(attr: TokenStream, ts: TokenStream) -> TokenStream {
- export::export(attr.into(), ts.into()).into()
+pub fn export(attr: TokenStream, input: TokenStream) -> TokenStream {
+ parse_macro_input!(attr as syn::parse::Nothing);
+ export::export(parse_macro_input!(input)).into()
}

/// Like [`core::format_args!`], but automatically wraps arguments in [`kernel::fmt::Adapter`].
--
2.51.2