Wedson Almeida Filho 851849824b rust: file: add Rust abstraction for struct file ... This abstraction makes it possible to manipulate the open files for a process. The new `File` struct wraps the C `struct file`. When accessing it using the smart pointer `ARef<File>`, the pointer will own a reference count to the file. When accessing it as `&File`, then the reference does not own a refcount, but the borrow checker will ensure that the reference count does not hit zero while the `&File` is live. Since this is intended to manipulate the open files of a process, we introduce an `fget` constructor that corresponds to the C `fget` method. In future patches, it will become possible to create a new fd in a process and bind it to a `File`. Rust Binder will use these to send fds from one process to another. We also provide a method for accessing the file's flags. Rust Binder will use this to access the flags of the Binder fd to check whether the non-blocking flag is set, which affects what the Binder ioctl does. This introduces a struct for the EBADF error type, rather than just using the Error type directly. This has two advantages: * `File::fget` returns a `Result<ARef<File>, BadFdError>`, which the compiler will represent as a single pointer, with null being an error. This is possible because the compiler understands that `BadFdError` has only one possible value, and it also understands that the `ARef<File>` smart pointer is guaranteed non-null. * Additionally, we promise to users of the method that the method can only fail with EBADF, which means that they can rely on this promise without having to inspect its implementation. That said, there are also two disadvantages: * Defining additional error types involves boilerplate. * The question mark operator will only utilize the `From` trait once, which prevents you from using the question mark operator on `BadFdError` in methods that return some third error type that the kernel `Error` is convertible into. (However, it works fine in methods that return `Error`.) Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com> Co-developed-by: Daniel Xu <dxu@dxuuu.xyz> Signed-off-by: Daniel Xu <dxu@dxuuu.xyz> Co-developed-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Benno Lossin <benno.lossin@proton.me> Signed-off-by: Alice Ryhl <aliceryhl@google.com> Link: https://lore.kernel.org/r/20240915-alice-file-v10-3-88484f7a3dcf@google.com Reviewed-by: Gary Guo <gary@garyguo.net> Signed-off-by: Christian Brauner <brauner@kernel.org>		2024-09-30 13:02:28 +02:00
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bindings	rust: file: add Rust abstraction for struct file	2024-09-30 13:02:28 +02:00
helpers	rust: file: add Rust abstraction for struct file	2024-09-30 13:02:28 +02:00
kernel	rust: file: add Rust abstraction for struct file	2024-09-30 13:02:28 +02:00
macros	kbuild: rust: replace proc macros dependency on core.o with the version text	2024-09-05 22:44:51 +02:00
uapi	rust: allow dead_code for never constructed bindings	2024-07-10 10:28:51 +02:00
.gitignore	rust: support running Rust documentation tests as KUnit ones	2023-07-19 09:32:53 -06:00
bindgen_parameters	rust: Ignore preserve-most functions	2023-12-13 01:09:55 +01:00
build_error.rs	rust: add build_error crate	2022-12-04 01:59:16 +01:00
compiler_builtins.rs	rust: add intrinsics to fix -Os builds	2024-08-10 00:05:10 +02:00
exports.c	rust: kbuild: auto generate helper exports	2024-08-19 11:09:02 +02:00
Makefile	kbuild: rust: replace proc macros dependency on core.o with the version text	2024-09-05 22:44:51 +02:00