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>
Add support for generic parameters defaults in `#[pin_data]` by using
the newly introduced `decl_generics` instead of the `impl_generics`.
Before this would not compile:
#[pin_data]
struct Foo<const N: usize = 0> {
// ...
}
because it would be expanded to this:
struct Foo<const N: usize = 0> {
// ...
}
const _: () = {
struct __ThePinData<const N: usize = 0> {
__phantom: ::core::marker::PhantomData<fn(Foo<N>) -> Foo<N>>,
}
impl<const N: usize = 0> ::core::clone::Clone for __ThePinData<N> {
fn clone(&self) -> Self {
*self
}
}
// [...] rest of expansion omitted
};
The problem is with the `impl<const N: usize = 0>`, since that is
invalid Rust syntax. It should not mention the default value at all,
since default values only make sense on type definitions.
The new `impl_generics` do not contain the default values, thus
generating correct Rust code.
This is used by the next commit that puts `#[pin_data]` on
`kernel::workqueue::Work`.
Signed-off-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Tested-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20240309155243.482334-2-benno.lossin@proton.me
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
The generic parameters on a type definition can specify default values.
Currently `parse_generics()` cannot handle this though. For example when
parsing the following generics:
<T: Clone, const N: usize = 0>
The `impl_generics` will be set to `T: Clone, const N: usize = 0` and
`ty_generics` will be set to `T, N`. Now using the `impl_generics` on an
impl block:
impl<$($impl_generics)*> Foo {}
will result in invalid Rust code, because default values are only
available on type definitions.
Therefore add parsing support for generic parameter default values using
a new kind of generics called `decl_generics` and change the old
behavior of `impl_generics` to not contain the generic parameter default
values.
Now `Generics` has three fields:
- `impl_generics`: the generics with bounds
(e.g. `T: Clone, const N: usize`)
- `decl_generics`: the generics with bounds and default values
(e.g. `T: Clone, const N: usize = 0`)
- `ty_generics`: contains the generics without bounds and without
default values (e.g. `T, N`)
`impl_generics` is designed to be used on `impl<$impl_generics>`,
`decl_generics` for the type definition, so `struct Foo<$decl_generics>`
and `ty_generics` whenever you use the type, so `Foo<$ty_generics>`.
Here is an example that uses all three different types of generics:
let (Generics { decl_generics, impl_generics, ty_generics }, rest) = parse_generics(input);
quote! {
struct Foo<$($decl_generics)*> {
// ...
}
impl<$impl_generics> Foo<$ty_generics> {
fn foo() {
// ...
}
}
}
The next commit contains a fix to the `#[pin_data]` macro making it
compatible with generic parameter default values by relying on this new
behavior.
Signed-off-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20240309155243.482334-1-benno.lossin@proton.me
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Other macros might also want to parse generics. Additionally this makes
the code easier to read, as the next commit will introduce more code in
`#[pin_data]`. Also add more comments to explain how parsing generics
work.
Signed-off-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Link: https://lore.kernel.org/r/20230424081112.99890-2-benno.lossin@proton.me
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Modules can (and usually do) have multiple alias tags, in order to
specify multiple possible device matches for autoloading. Allow this by
changing the alias ModuleInfo field to an Option<Vec<String>>.
Note: For normal device IDs this is autogenerated by modpost (which is
not properly integrated with Rust support yet), so it is useful to be
able to manually add device match aliases for now, and should still be
useful in the future for corner cases that modpost does not handle.
This pulls in the expect_group() helper from the rfl/rust branch
(with credit to authors).
Co-developed-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Co-developed-by: Finn Behrens <me@kloenk.dev>
Signed-off-by: Finn Behrens <me@kloenk.dev>
Co-developed-by: Sumera Priyadarsini <sylphrenadin@gmail.com>
Signed-off-by: Sumera Priyadarsini <sylphrenadin@gmail.com>
Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
Signed-off-by: Asahi Lina <lina@asahilina.net>
Link: https://lore.kernel.org/r/20230224-rust-macros-v2-1-7396e8b7018d@asahilina.net
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Instead of taking binary string literals, take string ones instead,
making it easier for users to define a module, i.e. instead of
calling `module!` like:
module! {
...
name: b"rust_minimal",
...
}
now it is called as:
module! {
...
name: "rust_minimal",
...
}
Module names, aliases and license strings are restricted to
ASCII only. However, the author and the description allows UTF-8.
For simplicity (avoid parsing), escape sequences and raw string
literals are not yet handled.
Link: https://github.com/Rust-for-Linux/linux/issues/252
Link: https://lore.kernel.org/lkml/YukvvPOOu8uZl7+n@yadro.com/
Signed-off-by: Gary Guo <gary@garyguo.net>
[Reworded, adapted for upstream and applied latest changes]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
This crate contains all the procedural macros ("proc macros")
shared by all the kernel.
Procedural macros allow to create syntax extensions. They run at
compile-time and can consume as well as produce Rust syntax.
For instance, the `module!` macro that is used by Rust modules
is implemented here. It allows to easily declare the equivalent
information to the `MODULE_*` macros in C modules, e.g.:
module! {
type: RustMinimal,
name: b"rust_minimal",
author: b"Rust for Linux Contributors",
description: b"Rust minimal sample",
license: b"GPL",
}
Co-developed-by: Alex Gaynor <alex.gaynor@gmail.com>
Signed-off-by: Alex Gaynor <alex.gaynor@gmail.com>
Co-developed-by: Finn Behrens <me@kloenk.de>
Signed-off-by: Finn Behrens <me@kloenk.de>
Co-developed-by: Adam Bratschi-Kaye <ark.email@gmail.com>
Signed-off-by: Adam Bratschi-Kaye <ark.email@gmail.com>
Co-developed-by: Wedson Almeida Filho <wedsonaf@google.com>
Signed-off-by: Wedson Almeida Filho <wedsonaf@google.com>
Co-developed-by: Sumera Priyadarsini <sylphrenadin@gmail.com>
Signed-off-by: Sumera Priyadarsini <sylphrenadin@gmail.com>
Co-developed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Gary Guo <gary@garyguo.net>
Co-developed-by: Matthew Bakhtiari <dev@mtbk.me>
Signed-off-by: Matthew Bakhtiari <dev@mtbk.me>
Co-developed-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Signed-off-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
