[PATCH v2 0/5] Check Rust signatures at compile time

Alice Ryhl
2025-02-28T12:40:07Z

Rust has two different tools for generating function declarations to
call across the FFI boundary:

* bindgen. Generates Rust declarations from a C header.
* cbindgen. Generates C headers from Rust declarations.

In the kernel, we only use bindgen. This is because cbindgen assumes a
cargo-based buildsystem, so it is not compatible with the kernel's build
system. This means that when C code calls a Rust function by name, its
signature must be duplicated in both Rust code and a C header, and the
signature needs to be kept in sync manually.

To eliminate this manual checking, introduce a new macro that verifies
at compile time that the two function declarations use the same
signature. The idea is to run the C declaration through bindgen, and
then have rustc verify that the function pointers have the same type.

The main commit of this series is "rust: add #[export] macro". Please
see its commit message for more details.

Signed-off-by: Alice Ryhl <aliceryhl@google.com>
---
Changes in v2:
- Various improvements to documentation.
- Split out quote! changes into its own commit.
- Link to v1: https://lore.kernel.org/r/20250227-export-macro-v1-0-948775fc37aa@google.com

---
Alice Ryhl (5):
rust: fix signature of rust_fmt_argument
rust: macros: support additional tokens in quote!
rust: add #[export] macro
print: use new #[export] macro for rust_fmt_argument
panic_qr: use new #[export] macro

drivers/gpu/drm/drm_panic.c | 5 -----
drivers/gpu/drm/drm_panic_qr.rs | 15 +++++++++++----
include/drm/drm_panic.h | 7 +++++++
include/linux/sprintf.h | 3 +++
lib/vsprintf.c | 3 ---
rust/bindings/bindings_helper.h | 4 ++++
rust/kernel/prelude.rs | 2 +-
rust/kernel/print.rs | 10 +++++-----
rust/macros/export.rs | 28 ++++++++++++++++++++++++++++
rust/macros/helpers.rs | 19 ++++++++++++++++++-
rust/macros/lib.rs | 24 ++++++++++++++++++++++++
rust/macros/quote.rs | 21 +++++++++++++++++++--
12 files changed, 120 insertions(+), 21 deletions(-)
---
base-commit: a64dcfb451e254085a7daee5fe51bf22959d52d3
change-id: 20250227-export-macro-9aa9f1016d8c

Best regards,
--
Alice Ryhl <aliceryhl@google.com>