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Diffstat (limited to 'Documentation/rust/general-information.rst')
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diff --git a/Documentation/rust/general-information.rst b/Documentation/rust/general-information.rst index 081397827a7e..4bb6ac12d482 100644 --- a/Documentation/rust/general-information.rst +++ b/Documentation/rust/general-information.rst @@ -64,6 +64,63 @@ but it is intended that coverage is expanded as time goes on. "Leaf" modules (e.g. drivers) should not use the C bindings directly. Instead, subsystems should provide as-safe-as-possible abstractions as needed. +.. code-block:: + + rust/bindings/ + (rust/helpers.c) + + include/ -----+ <-+ + | | + drivers/ rust/kernel/ +----------+ <-+ | + fs/ | bindgen | | + .../ +-------------------+ +----------+ --+ | + | Abstractions | | | + +---------+ | +------+ +------+ | +----------+ | | + | my_foo | -----> | | foo | | bar | | -------> | Bindings | <-+ | + | driver | Safe | | sub- | | sub- | | Unsafe | | | + +---------+ | |system| |system| | | bindings | <-----+ + | | +------+ +------+ | | crate | | + | | kernel crate | +----------+ | + | +-------------------+ | + | | + +------------------# FORBIDDEN #--------------------------------+ + +The main idea is to encapsulate all direct interaction with the kernel's C APIs +into carefully reviewed and documented abstractions. Then users of these +abstractions cannot introduce undefined behavior (UB) as long as: + +#. The abstractions are correct ("sound"). +#. Any ``unsafe`` blocks respect the safety contract necessary to call the + operations inside the block. Similarly, any ``unsafe impl``\ s respect the + safety contract necessary to implement the trait. + +Bindings +~~~~~~~~ + +By including a C header from ``include/`` into +``rust/bindings/bindings_helper.h``, the ``bindgen`` tool will auto-generate the +bindings for the included subsystem. After building, see the ``*_generated.rs`` +output files in the ``rust/bindings/`` directory. + +For parts of the C header that ``bindgen`` does not auto generate, e.g. C +``inline`` functions or non-trivial macros, it is acceptable to add a small +wrapper function to ``rust/helpers.c`` to make it available for the Rust side as +well. + +Abstractions +~~~~~~~~~~~~ + +Abstractions are the layer between the bindings and the in-kernel users. They +are located in ``rust/kernel/`` and their role is to encapsulate the unsafe +access to the bindings into an as-safe-as-possible API that they expose to their +users. Users of the abstractions include things like drivers or file systems +written in Rust. + +Besides the safety aspect, the abstractions are supposed to be "ergonomic", in +the sense that they turn the C interfaces into "idiomatic" Rust code. Basic +examples are to turn the C resource acquisition and release into Rust +constructors and destructors or C integer error codes into Rust's ``Result``\ s. + Conditional compilation ----------------------- |