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Thu, 27 Feb 2025 09:02:42 -0800 (PST) Date: Thu, 27 Feb 2025 17:02:00 +0000 In-Reply-To: <20250227-export-macro-v1-0-948775fc37aa@google.com> Mime-Version: 1.0 References: <20250227-export-macro-v1-0-948775fc37aa@google.com> X-Developer-Key: i=aliceryhl@google.com; a=openpgp; fpr=49F6C1FAA74960F43A5B86A1EE7A392FDE96209F X-Developer-Signature: v=1; a=openpgp-sha256; l=7286; i=aliceryhl@google.com; h=from:subject:message-id; bh=TeIglh23ISS4+Bdf8fwiVWAv4hzE5dSrVK2+5fzc9Q4=; b=owEBbAKT/ZANAwAKAQRYvu5YxjlGAcsmYgBnwJqqKr8/onOvuGjaOiYUGmqozHC77FCgBSok4 nPET3stwHaJAjIEAAEKAB0WIQSDkqKUTWQHCvFIvbIEWL7uWMY5RgUCZ8CaqgAKCRAEWL7uWMY5 RitPD/df0G8ivb0s8H1GZAyBpLj9Ic/1m5Re3XwiQcTT1V21Xh3S4Lvjue6PX/niFQsEJYdCofH kQDXIyYLK+u2jF7/IJ15TuvhMuSgZWuReLcazWLkvCU5bR7DXejkkfUxpMWngszVyo5Hy9/fdiS NLpxymgICMdUuomMdfTHaGLmhD2Z3B30Le9kQLo2DNkf108z9nFXGaPdy006lQnd0n6xyao8Mf5 LAo7oTuYw3kFAXPMBKyZGgWx/Y6cv9iD/3kBd6PQofrEbL7bITBQZulZ1VQEM+3lTnvmoz3AaHy HRxqJulYVZ2VKpMrOBQhbqLyKS0SzZ/D3LuwoOvhCzka2yNUxqyAjWVG1ls6JYCEqySN53mvkNy Ihtmwng10x2KiOFZtY7PGzNZKufO1+iIfJbc8BeiSvvYa6pmQoh79cO0FeRqkM2fjgzVcD39BDq LPYIlAJ2i1hVaRulVaj5Z+6Jq19XnPqNTfnn/YvkGFhw51yv6WsuGi6zRMMpuLhfWzkcpVDEOk1 tY5nLAftB3kFq2IGMfXHov2BEIWgzrORXG1keq7ij50N1Sf/zdL5hyRuVOsZ/hR0QH3hPR4PGXj ndhAjBFXZPqL10srqO8k/iuLFIwCweZ6UrLnJde0Ho/vv3rmhRAnAzElmOz5Iz4vffvRnaItlVn hOS4J2pFaD/02 X-Mailer: b4 0.14.1 Message-ID: <20250227-export-macro-v1-2-948775fc37aa@google.com> Subject: [PATCH 2/4] rust: add #[export] macro From: Alice Ryhl To: Greg Kroah-Hartman , Miguel Ojeda Cc: Petr Mladek , Steven Rostedt , Andy Shevchenko , Rasmus Villemoes , Sergey Senozhatsky , Andrew Morton , Boqun Feng , Gary Guo , " =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= " , Benno Lossin , Andreas Hindborg , Trevor Gross , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, dri-devel@lists.freedesktop.org, Alice Ryhl X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" This macro behaves like #[no_mangle], but also performs an assertion that the Rust function has the same signature as what is declared in the C header. If the signatures don't match, you will get errors that look like this: error[E0308]: `if` and `else` have incompatible types --> /rust/kernel/print.rs:22:22 | 21 | #[export] | --------- expected because of this 22 | unsafe extern "C" fn rust_fmt_argument( | ^^^^^^^^^^^^^^^^^ expected `u8`, found `i8` | = note: expected fn item `unsafe extern "C" fn(*mut u8, *mut u8, *mut c_void) -> *mut u8 {bindings::rust_fmt_argument}` found fn item `unsafe extern "C" fn(*mut i8, *mut i8, *const c_void) -> *mut i8 {print::rust_fmt_argument}` Signed-off-by: Alice Ryhl --- rust/kernel/prelude.rs | 2 +- rust/macros/export.rs | 25 +++++++++++++++++++++++++ rust/macros/helpers.rs | 19 ++++++++++++++++++- rust/macros/lib.rs | 18 ++++++++++++++++++ rust/macros/quote.rs | 21 +++++++++++++++++++-- 5 files changed, 81 insertions(+), 4 deletions(-) diff --git a/rust/kernel/prelude.rs b/rust/kernel/prelude.rs index dde2e0649790..889102f5a81e 100644 --- a/rust/kernel/prelude.rs +++ b/rust/kernel/prelude.rs @@ -17,7 +17,7 @@ pub use crate::alloc::{flags::*, Box, KBox, KVBox, KVVec, KVec, VBox, VVec, Vec}; #[doc(no_inline)] -pub use macros::{module, pin_data, pinned_drop, vtable, Zeroable}; +pub use macros::{export, module, pin_data, pinned_drop, vtable, Zeroable}; pub use super::{build_assert, build_error}; diff --git a/rust/macros/export.rs b/rust/macros/export.rs new file mode 100644 index 000000000000..3398e1655124 --- /dev/null +++ b/rust/macros/export.rs @@ -0,0 +1,25 @@ +// SPDX-License-Identifier: GPL-2.0 + +use crate::helpers::function_name; +use proc_macro::TokenStream; + +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::() + .unwrap(); + }; + + let signature_check = quote!( + const _: () = { + if true { + ::kernel::bindings::#name + } else { + #name + }; + }; + ); + + let no_mangle = "#[no_mangle]".parse::().unwrap(); + TokenStream::from_iter([signature_check, no_mangle, ts]) +} diff --git a/rust/macros/helpers.rs b/rust/macros/helpers.rs index 563dcd2b7ace..3e04f8ecfc74 100644 --- a/rust/macros/helpers.rs +++ b/rust/macros/helpers.rs @@ -1,6 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 -use proc_macro::{token_stream, Group, TokenStream, TokenTree}; +use proc_macro::{token_stream, Group, Ident, TokenStream, TokenTree}; pub(crate) fn try_ident(it: &mut token_stream::IntoIter) -> Option { if let Some(TokenTree::Ident(ident)) = it.next() { @@ -215,3 +215,20 @@ pub(crate) fn parse_generics(input: TokenStream) -> (Generics, Vec) { rest, ) } + +/// Given a function declaration, finds the name of the function. +pub(crate) fn function_name(input: TokenStream) -> Option { + 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 +} diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs index d61bc6a56425..3cbf7705c4c1 100644 --- a/rust/macros/lib.rs +++ b/rust/macros/lib.rs @@ -9,6 +9,7 @@ #[macro_use] mod quote; mod concat_idents; +mod export; mod helpers; mod module; mod paste; @@ -174,6 +175,23 @@ pub fn vtable(attr: TokenStream, ts: TokenStream) -> TokenStream { vtable::vtable(attr, ts) } +/// Export a function so that C code can call it. +/// +/// This macro has the following effect: +/// +/// * Disables name mangling for this function. +/// * Verifies at compile-time that the function signature matches what's in the header file. +/// +/// This macro requires that the function is mentioned in a C header file, and that the header file +/// is included in `rust/bindings/bindings_helper.h`. +/// +/// This macro is *not* the same as the C macro `EXPORT_SYMBOL*`, since 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, ts) +} + /// Concatenate two identifiers. /// /// This is useful in macros that need to declare or reference items with names diff --git a/rust/macros/quote.rs b/rust/macros/quote.rs index 33a199e4f176..c18960a91082 100644 --- a/rust/macros/quote.rs +++ b/rust/macros/quote.rs @@ -20,6 +20,12 @@ fn to_tokens(&self, tokens: &mut TokenStream) { } } +impl ToTokens for proc_macro::Ident { + fn to_tokens(&self, tokens: &mut TokenStream) { + tokens.extend([TokenTree::from(self.clone())]); + } +} + impl ToTokens for TokenTree { fn to_tokens(&self, tokens: &mut TokenStream) { tokens.extend([self.clone()]); @@ -40,7 +46,7 @@ fn to_tokens(&self, tokens: &mut TokenStream) { /// `quote` crate but provides only just enough functionality needed by the current `macros` crate. macro_rules! quote_spanned { ($span:expr => $($tt:tt)*) => {{ - let mut tokens; + let mut tokens: ::std::vec::Vec<::proc_macro::TokenTree>; #[allow(clippy::vec_init_then_push)] { tokens = ::std::vec::Vec::new(); @@ -65,7 +71,8 @@ macro_rules! quote_spanned { quote_spanned!(@proc $v $span $($tt)*); }; (@proc $v:ident $span:ident ( $($inner:tt)* ) $($tt:tt)*) => { - let mut tokens = ::std::vec::Vec::new(); + #[allow(unused_mut)] + let mut tokens = ::std::vec::Vec::<::proc_macro::TokenTree>::new(); quote_spanned!(@proc tokens $span $($inner)*); $v.push(::proc_macro::TokenTree::Group(::proc_macro::Group::new( ::proc_macro::Delimiter::Parenthesis, @@ -136,6 +143,16 @@ 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 _ $($tt:tt)*) => { + $v.push(::proc_macro::TokenTree::Ident(::proc_macro::Ident::new("_", $span))); + 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)*);