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

[Alice Ryhl]

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 at 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 at google.com>