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a=ed25519-sha256; t=1765845890; l=10908; i=mmaurer@google.com; s=20250429; h=from:subject:message-id; bh=eJzzXyTehyDOrkdA4s2sZqkwAreYcpT1LVD5yuHGCEg=; b=9udXk9G1Dt7+BmcMMAc+ksdY1kYgvCDrvn2/pYGVJNNN24pKAJAmnOVsaftEkpz6lfgfYo9fx GhEmAzrI3tGCqrxK1FPXWRJpUApNy7EOA3hKdERdIscJ2MwWvPB8w+i X-Mailer: b4 0.14.2 Message-ID: <20251216-transmute-v2-3-b23e5277ad02@google.com> Subject: [PATCH v2 3/3] rust: Support deriving `AsBytes`/`FromBytes` on bindgen types From: Matthew Maurer To: Miguel Ojeda , Boqun Feng , Gary Guo , "=?utf-8?q?Bj=C3=B6rn_Roy_Baron?=" , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich Cc: rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, Matthew Maurer Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable To support this, we need to move the `transmute` module into a separate crate to allow the `bindings` crate to depend on it. Most user code is still expected to address the module as `kernel::transmute`, which is a re-export. `ffi::transmute` is now available for use in `bindings`. Signed-off-by: Matthew Maurer --- rust/Makefile | 14 +++++++++----- rust/bindgen_parameters | 8 ++++++++ rust/bindings/lib.rs | 4 ++++ rust/{ffi.rs =3D> ffi/lib.rs} | 5 +++++ rust/{kernel =3D> ffi}/transmute.rs | 0 rust/kernel/lib.rs | 2 +- rust/macros/lib.rs | 24 ++++++++++++++++++++++-- rust/macros/transmute.rs | 12 +++++++----- rust/uapi/lib.rs | 4 ++++ scripts/generate_rust_analyzer.py | 2 +- 10 files changed, 61 insertions(+), 14 deletions(-) diff --git a/rust/Makefile b/rust/Makefile index 5d357dce1704d15e43effc528be8f5a4d74d3d8d..178aa3036c4acba1c4c26619691= 2da2d60fe0d5f 100644 --- a/rust/Makefile +++ b/rust/Makefile @@ -207,7 +207,7 @@ rustdoc-compiler_builtins: $(src)/compiler_builtins.rs = rustdoc-core FORCE +$(call if_changed,rustdoc) =20 rustdoc-ffi: private is-kernel-object :=3D y -rustdoc-ffi: $(src)/ffi.rs rustdoc-core FORCE +rustdoc-ffi: $(src)/ffi/lib.rs rustdoc-core FORCE +$(call if_changed,rustdoc) =20 rustdoc-pin_init_internal: private rustdoc_host =3D yes @@ -249,7 +249,7 @@ quiet_cmd_rustc_test_library =3D $(RUSTC_OR_CLIPPY_QUIE= T) TL $< rusttestlib-build_error: $(src)/build_error.rs FORCE +$(call if_changed,rustc_test_library) =20 -rusttestlib-ffi: $(src)/ffi.rs FORCE +rusttestlib-ffi: $(src)/ffi/lib.rs FORCE +$(call if_changed,rustc_test_library) =20 rusttestlib-proc_macro2: private rustc_target_flags =3D $(proc_macro2-flag= s) @@ -657,22 +657,26 @@ $(obj)/build_error.o: $(src)/build_error.rs $(obj)/co= mpiler_builtins.o FORCE +$(call if_changed_rule,rustc_library) =20 $(obj)/ffi.o: private skip_gendwarfksyms =3D 1 -$(obj)/ffi.o: $(src)/ffi.rs $(obj)/compiler_builtins.o FORCE +$(obj)/ffi.o: $(src)/ffi/lib.rs $(obj)/compiler_builtins.o FORCE +$(call if_changed_rule,rustc_library) =20 -$(obj)/bindings.o: private rustc_target_flags =3D --extern ffi --extern pi= n_init +$(obj)/bindings.o: private rustc_target_flags =3D --extern ffi --extern pi= n_init \ + --extern macros $(obj)/bindings.o: $(src)/bindings/lib.rs \ $(obj)/ffi.o \ $(obj)/pin_init.o \ + $(obj)/$(libmacros_name) \ $(obj)/bindings/bindings_generated.rs \ $(obj)/bindings/bindings_helpers_generated.rs FORCE +$(call if_changed_rule,rustc_library) =20 -$(obj)/uapi.o: private rustc_target_flags =3D --extern ffi --extern pin_in= it +$(obj)/uapi.o: private rustc_target_flags =3D --extern ffi --extern pin_in= it \ + --extern macros $(obj)/uapi.o: private skip_gendwarfksyms =3D 1 $(obj)/uapi.o: $(src)/uapi/lib.rs \ $(obj)/ffi.o \ $(obj)/pin_init.o \ + $(obj)/$(libmacros_name) \ $(obj)/uapi/uapi_generated.rs FORCE +$(call if_changed_rule,rustc_library) =20 diff --git a/rust/bindgen_parameters b/rust/bindgen_parameters index fd2fd1c3cb9a51ea46fcd721907783b457aa1378..d56343ca03979e345f8adb7eb8f= d7f2b9d4be6ee 100644 --- a/rust/bindgen_parameters +++ b/rust/bindgen_parameters @@ -64,3 +64,11 @@ # Structs should implement `Zeroable` when all of their fields do. --with-derive-custom-struct .*=3DMaybeZeroable --with-derive-custom-union .*=3DMaybeZeroable + +# Every C struct can try to derive FromBytes. If they have unmet requireme= nts, +# the impl will just be a no-op due to the where clause. +--with-derive-custom-struct .*=3DFromBytesFfi + +# We can't auto-derive AsBytes, as we need a const-time check to see if th= ere +# is padding involved. Add it explicitly when you expect no padding. +--with-derive-custom-struct cpumask=3DAsBytesFfi diff --git a/rust/bindings/lib.rs b/rust/bindings/lib.rs index 0c57cf9b4004f176997c59ecc58a9a9ac76163d9..c29312fca1b01b707bb11b05d44= 6d44480a4b81f 100644 --- a/rust/bindings/lib.rs +++ b/rust/bindings/lib.rs @@ -31,6 +31,10 @@ #[allow(clippy::undocumented_unsafe_blocks)] #[cfg_attr(CONFIG_RUSTC_HAS_UNNECESSARY_TRANSMUTES, allow(unnecessary_tran= smutes))] mod bindings_raw { + use macros::{ + AsBytesFfi, + FromBytesFfi, // + }; use pin_init::{MaybeZeroable, Zeroable}; =20 // Manual definition for blocklisted types. diff --git a/rust/ffi.rs b/rust/ffi/lib.rs similarity index 87% rename from rust/ffi.rs rename to rust/ffi/lib.rs index f961e9728f590fd2c52d4c03a1f715d654051d04..14052362f091a609bc505fe6eca= 77fe998fe2321 100644 --- a/rust/ffi.rs +++ b/rust/ffi/lib.rs @@ -10,6 +10,11 @@ =20 #![no_std] =20 +#[doc(hidden)] +// This lives here to make it accessible to `bindings`, similar to the oth= er `ffi` types. +// User code should access it through `kernel::transmute`. +pub mod transmute; + macro_rules! alias { ($($name:ident =3D $ty:ty;)*) =3D> {$( #[allow(non_camel_case_types, missing_docs)] diff --git a/rust/kernel/transmute.rs b/rust/ffi/transmute.rs similarity index 100% rename from rust/kernel/transmute.rs rename to rust/ffi/transmute.rs diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index f812cf12004286962985a068665443dc22c389a2..4aa54dd83319ef16bd4baa19641= 14f1e6549942b 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -63,6 +63,7 @@ extern crate self as kernel; =20 pub use ffi; +pub use ffi::transmute; =20 pub mod acpi; pub mod alloc; @@ -146,7 +147,6 @@ pub mod task; pub mod time; pub mod tracepoint; -pub mod transmute; pub mod types; pub mod uaccess; #[cfg(CONFIG_USB =3D "y")] diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs index d66397942529f67697f74a908e257cacc4201d84..bde94c2a8ddf708872bcd56a471= 3784b5ccdf04e 100644 --- a/rust/macros/lib.rs +++ b/rust/macros/lib.rs @@ -506,7 +506,7 @@ pub fn kunit_tests(attr: TokenStream, ts: TokenStream) = -> TokenStream { #[proc_macro_derive(FromBytes)] pub fn derive_from_bytes(tokens: TokenStream) -> TokenStream { let input =3D parse_macro_input!(tokens as DeriveInput); - transmute::from_bytes(input).into() + transmute::from_bytes("kernel", input).into() } =20 /// Implements `AsBytes` for a struct. @@ -536,5 +536,25 @@ pub fn derive_from_bytes(tokens: TokenStream) -> Token= Stream { #[proc_macro_derive(AsBytes)] pub fn derive_as_bytes(tokens: TokenStream) -> TokenStream { let input =3D parse_macro_input!(tokens as DeriveInput); - transmute::as_bytes(input).into() + transmute::as_bytes("kernel", input).into() +} + +#[doc(hidden)] +#[proc_macro_derive(FromBytesFfi)] +/// This is equivalent to `FromBytes`, but uses the `ffi` crate as the tra= it definition site +/// instead of `kernel`. This is intended for use inside `bindings`. Every= one else can refer to the +/// trait through `kernel`. +pub fn derive_from_bytes_trait(tokens: TokenStream) -> TokenStream { + let input =3D parse_macro_input!(tokens as DeriveInput); + transmute::from_bytes("ffi", input).into() +} + +#[doc(hidden)] +#[proc_macro_derive(AsBytesFfi)] +/// This is equivalent to `AsBytes`, but uses the `ffi` crate as the trait= definition site +/// instead of `kernel`. This is intended for use inside `bindings`. Every= one else can refer to the +/// trait through `kernel`. +pub fn derive_as_bytes_trait(tokens: TokenStream) -> TokenStream { + let input =3D parse_macro_input!(tokens as DeriveInput); + transmute::as_bytes("ffi", input).into() } diff --git a/rust/macros/transmute.rs b/rust/macros/transmute.rs index 43cf36a1334f1fed23c0e777026392f987f78d8d..9bd6d279675fb1d58cdceff1f4d= de0dcf33fbf99 100644 --- a/rust/macros/transmute.rs +++ b/rust/macros/transmute.rs @@ -1,6 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 =20 -use proc_macro2::TokenStream; +use proc_macro2::{Span, TokenStream}; use syn::{parse_quote, DeriveInput, Fields, Ident, ItemConst, Path, WhereC= lause}; =20 fn all_fields_impl(fields: &Fields, trait_: &Path) -> WhereClause { @@ -19,7 +19,8 @@ fn struct_padding_check(fields: &Fields, name: &Ident) ->= ItemConst { } } =20 -pub(crate) fn as_bytes(input: DeriveInput) -> TokenStream { +pub(crate) fn as_bytes(crate_: &str, input: DeriveInput) -> TokenStream { + let crate_ =3D Ident::new(crate_, Span::call_site()); if !input.generics.params.is_empty() { return quote::quote! { compile_error!("#[derive(AsBytes)] does not= support generics") }; } @@ -27,7 +28,7 @@ pub(crate) fn as_bytes(input: DeriveInput) -> TokenStream= { return quote::quote! { compile_error!("#[derive(AsBytes)] only sup= ports structs") }; }; let name =3D input.ident; - let trait_ =3D parse_quote! { ::kernel::transmute::AsBytes }; + let trait_ =3D parse_quote! { ::#crate_::transmute::AsBytes }; let where_clause =3D all_fields_impl(&ds.fields, &trait_); let padding_check =3D struct_padding_check(&ds.fields, &name); quote::quote! { @@ -37,13 +38,14 @@ unsafe impl #trait_ for #name #where_clause {} } } =20 -pub(crate) fn from_bytes(input: DeriveInput) -> TokenStream { +pub(crate) fn from_bytes(crate_: &str, input: DeriveInput) -> TokenStream { + let crate_ =3D Ident::new(crate_, Span::call_site()); let syn::Data::Struct(ref ds) =3D &input.data else { return quote::quote! { compile_error!("#[derive(FromBytes)] only s= upports structs") }; }; let (impl_generics, ty_generics, base_where_clause) =3D input.generics= .split_for_impl(); let name =3D input.ident; - let trait_ =3D parse_quote! { ::kernel::transmute::FromBytes }; + let trait_ =3D parse_quote! { ::#crate_::transmute::FromBytes }; let mut where_clause =3D all_fields_impl(&ds.fields, &trait_); if let Some(base_clause) =3D base_where_clause { where_clause diff --git a/rust/uapi/lib.rs b/rust/uapi/lib.rs index 1d5fd9efb93e9db97fec84fca2bae37b500c20c5..2033b7125558d7ccfae67b94777= f5ce59593a528 100644 --- a/rust/uapi/lib.rs +++ b/rust/uapi/lib.rs @@ -34,6 +34,10 @@ type __kernel_ssize_t =3D isize; type __kernel_ptrdiff_t =3D isize; =20 +use macros::{ + AsBytesFfi, + FromBytesFfi, // +}; use pin_init::MaybeZeroable; =20 include!(concat!(env!("OBJTREE"), "/rust/uapi/uapi_generated.rs")); diff --git a/scripts/generate_rust_analyzer.py b/scripts/generate_rust_anal= yzer.py index 147d0cc940681426771db865bc2462e7029a6d7d..843d081eacaca8edeeac5978bd8= 107a498008186 100755 --- a/scripts/generate_rust_analyzer.py +++ b/scripts/generate_rust_analyzer.py @@ -137,7 +137,7 @@ def generate_crates(srctree, objtree, sysroot_src, exte= rnal_src, cfgs, core_edit =20 append_crate( "ffi", - srctree / "rust" / "ffi.rs", + srctree / "rust" / "ffi" / "lib.rs", ["core", "compiler_builtins"], ) =20 --=20 2.52.0.305.g3fc767764a-goog