Previously, the `ForeignOwnable` trait had a method called `borrow_mut`
that was intended to provide mutable access to the inner value. However,
the method accidentally made it possible to change the address of the
object being modified, which usually isn't what we want. (And when we
want that, it can be done by calling `from_foreign` and `into_foreign`,
like how the old `borrow_mut` was implemented.)
In this patch, we introduce an alternate definition of `borrow_mut` that
solves the previous problem. Conceptually, given a pointer type `P` that
implements `ForeignOwnable`, the `borrow_mut` method gives you the same
kind of access as an `&mut P` would, except that it does not let you
change the pointer `P` itself.
This is analogous to how the existing `borrow` method provides the same
kind of access to the inner value as an `&P`.
Note that for types like `Arc`, having an `&mut Arc<T>` only gives you
immutable access to the inner `T`. This is because mutable references
assume exclusive access, but there might be other handles to the same
reference counted value, so the access isn't exclusive. The `Arc` type
implements this by making `borrow_mut` return the same type as `borrow`.
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20241120-borrow-mut-v6-6-80dbadd00951@gmail.com
[ Updated to `crate::ffi::`. Reworded title slightly. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
The `kernel` crate relies on both `coerce_unsized` and `dispatch_from_dyn`
unstable features.
Alice Ryhl has proposed [1] the introduction of the unstable macro
`SmartPointer` to reduce such dependence, along with a RFC patch [2].
Since Rust 1.81.0 this macro, later renamed to `CoercePointee` in
Rust 1.84.0 [3], has been fully implemented with the naming discussion
resolved.
This feature is now on track to stabilization in the language.
In order to do so, we shall start using this macro in the `kernel` crate
to prove the functionality and utility of the macro as the justification
of its stabilization.
This patch makes this switch in such a way that the crate remains
backward compatible with older Rust compiler versions,
via the new Kconfig option `RUSTC_HAS_COERCE_POINTEE`.
A minimal demonstration example is added to the
`samples/rust/rust_print_main.rs` module.
Link: https://rust-lang.github.io/rfcs/3621-derive-smart-pointer.html [1]
Link: https://lore.kernel.org/all/20240823-derive-smart-pointer-v1-1-53769cd37239@google.com/ [2]
Link: https://github.com/rust-lang/rust/pull/131284 [3]
Signed-off-by: Xiangfei Ding <dingxiangfei2009@gmail.com>
Reviewed-by: Fiona Behrens <me@kloenk.dev>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20241203205050.679106-2-dingxiangfei2009@gmail.com
[ Fixed version to 1.84. Renamed option to `RUSTC_HAS_COERCE_POINTEE`
to match `CC_HAS_*` ones. Moved up new config option, closer to the
`CC_HAS_*` ones. Simplified Kconfig line. Fixed typos and slightly
reworded example and commit. Added Link to PR. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Remove `unwrap` in asserts and replace it with `Option::Some`
matching. By doing it this way, the examples are more
descriptive, so it disambiguates the return type of
the `get(...)` and `next(...)`, because the `unwrap(...)`
can also be called on `Result`.
Signed-off-by: Daniel Sedlak <daniel@sedlak.dev>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20241123095033.41240-3-daniel@sedlak.dev
[ Reworded title slightly. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Because the `macros` crate exposes procedural macros, it must be
compiled as a dynamic library (so it can be loaded by the compiler at
compile-time).
Before this change the resulting artifact was always named
`libmacros.so`, which works on hosts where this matches the naming
convention for dynamic libraries. However the proper name on macOS would
be `libmacros.dylib`.
This turns out to matter even when the dependency is passed with a path
(`--extern macros=path/to/libmacros.so` rather than `--extern macros`)
because rustc uses the file name to infer the type of the library (see
link). This is because there's no way to specify both the path to and
the type of the external library via CLI flags. The compiler could
speculatively parse the file to determine its type, but it does not do
so today.
This means that libraries that match neither rustc's naming convention
for static libraries nor the platform's naming convention for dynamic
libraries are *rejected*.
The only solution I've found is to follow the host platform's naming
convention. This patch does that by querying the compiler to determine
the appropriate name for the artifact. This allows the kernel to build
with CONFIG_RUST=y on macOS.
Link: https://github.com/rust-lang/rust/blob/d829780/compiler/rustc_metadata/src/locator.rs#L728-L752
Tested-by: Daniel Gomez <da.gomez@samsung.com>
Co-developed-by: Fiona Behrens <me@kloenk.dev>
Signed-off-by: Fiona Behrens <me@kloenk.dev>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
Link: https://lore.kernel.org/r/20241216-b4-dylib-host-macos-v7-1-cfc507681447@gmail.com
[ Added `MAKEFLAGS=`s to avoid jobserver warnings. Removed space.
Reworded title. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
The sibling `build_assert!` is already in the prelude, it makes sense
that a "core"/"language" facility like this is part of the prelude and
users should not be defining their own one (thus there should be no risk
of future name collisions and we would want to be aware of them anyway).
Thus add `build_error!` into the prelude.
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20241123222849.350287-3-ojeda@kernel.org
[ Applied the change to the new miscdevice cases. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Users were using the hidden exported `kernel::build_error` function
instead of the intended `kernel::build_error!` macro, e.g. see the
previous commit.
To force to use the macro, move it into the `build_assert` module,
thus making it a compilation error and avoiding a collision in the same
"namespace". Using the function now would require typing the module name
(which is hidden), not just a single character.
Now attempting to use the function will trigger this error with the
right suggestion by the compiler:
error[E0423]: expected function, found macro `kernel::build_error`
--> samples/rust/rust_minimal.rs:29:9
|
29 | kernel::build_error();
| ^^^^^^^^^^^^^^^^^^^ not a function
|
help: use `!` to invoke the macro
|
29 | kernel::build_error!();
| +
An alternative would be using an alias, but it would be more complex
and moving it into the module seems right since it belongs there and
reduces the amount of code at the crate root.
Keep the `#[doc(hidden)]` inside `build_assert` in case the module is
not hidden in the future.
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20241123222849.350287-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Running Clippy for `rusttest` code is useful to catch issues there too,
even if the code is not as critical. In the future, this code may also
run in kernelspace and could be copy-pasted. Thus it is useful to keep
it under the same standards. For instance, it will now make us add
`// SAFETY` comments.
It also makes everything more consistent.
Thus clean the few issues spotted by Clippy and start running it.
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20241123180639.260191-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Clippy's lints may avoid emitting a suggestion to use a language or
library feature that is not supported by the minimum supported version,
if given by the `msrv` field in the configuration file.
For instance, Clippy should not suggest using `let ... else` in a lint
if the MSRV did not implement that syntax.
If the MSRV is not provided, Clippy will assume all features are available.
Thus enable it with the minimum Rust version the kernel supports.
Note that there is currently a small disadvantage in doing so: since
we still use unstable features that nevertheless work in the range
of versions we support (e.g. `#[expect(...)]`), we lose suggestions
for those. However, over time we will stop using unstable features
(especially language and library ones) as it is our goal, thus, in the
end, we will want to have the `msrv` set.
Rust is also considering adding a similar feature in `rustc` too, which
we should probably enable if it becomes available [2].
Link: 8298da72e7/clippy_utils/src/msrvs.rs (L20) [1]
Link: https://github.com/rust-lang/compiler-team/issues/772 [2]
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20241123222345.346976-1-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
