mirror of https://github.com/torvalds/linux.git
44e333fe46
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.
However, we only use bindgen in the kernel. 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.
Introducing cbindgen as a mandatory dependency to build the kernel would
be a rather complex and large change, so we do not consider that at this
time. Instead, 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 signature must still be written twice, but at least you can no
longer get it wrong. If the signatures don't match, you will get errors
that look like this:
error[E0308]: `if` and `else` have incompatible types
--> <linux>/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}`
It is unfortunate that the error message starts out by saying "`if` and
`else` have incompatible types", but I believe the rest of the error
message is reasonably clear and not too confusing.
Reviewed-by: Tamir Duberstein <tamird@gmail.com>
Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20250303-export-macro-v3-3-41fbad85a27f@google.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
|
||
|---|---|---|
| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.