pm24.git, branch rust-6.14

kbuild: rust: add PROCMACROLDFLAGS

2025-01-15T08:53:54Z

These are flags to be passed when linking proc macros for the Rust toolchain. If unset, it defaults to $(KBUILD_HOSTLDFLAGS). This is needed because the list of flags to link hostprogs is not necessarily the same as the list of flags used to link libmacros.so. When we build proc macros, we need the latter, not the former (e.g. when using a Rust compiler binary linked to a different C library than host programs). To distinguish between the two, introduce this new variable to stand out from KBUILD_HOSTLDFLAGS used to link other host progs. Signed-off-by: HONG Yifan Link: https://lore.kernel.org/r/20241017210430.2401398-2-elsk@google.com [ v3: - `export`ed the variable. Otherwise it would not be visible in `rust/Makefile`. - Removed "additional" from the documentation and commit message, since this actually replaces the other flags, unlike other cases. - Added example of use case to documentation and commit message. Thanks Alice for the details on what Google needs! - Instead of `HOSTLDFLAGS`, used `KBUILD_HOSTLDFLAGS` as the fallback to preserve the previous behavior as much as possible, as discussed with Alice/Yifan. Thus moved the variable down too (currently we do not modify `KBUILD_HOSTLDFLAGS` elsewhere) and avoided mentioning `HOSTLDFLAGS` directly in the documentation. - Fixed documentation header formatting. - Reworded slightly. - Miguel ] Tested-by: Alice Ryhl Reviewed-by: Alice Ryhl Reviewed-by: HONG Yifan Acked-by: Masahiro Yamada Link: https://lore.kernel.org/r/20241112184455.855133-1-ojeda@kernel.org Signed-off-by: Miguel Ojeda

rust: uaccess: generalize userSliceReader to support any Vec

2025-01-13T22:46:23Z

The UserSliceReader::read_all function is currently restricted to use only Vec with the kmalloc allocator. However, there is no reason for this limitation. This patch generalizes the function to accept any Vec regardless of the allocator used. There's a use-case for a KVVec in Binder to avoid maximum sizes for a certain array. Link: https://github.com/Rust-for-Linux/linux/issues/1136 Signed-off-by: Filipe Xavier Reviewed-by: Alice Ryhl Reviewed-by: Boqun Feng Link: https://lore.kernel.org/r/20250107-gen-userslice-readall-alloc-v2-1-d7fe4d19241a@gmail.com [ Reflowed and slightly reworded title. - Miguel ] Signed-off-by: Miguel Ojeda

rust: kernel: add improved version of `ForeignOwnable::borrow_mut`

2025-01-13T22:46:07Z

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` 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 Reviewed-by: Boqun Feng Reviewed-by: Benno Lossin Reviewed-by: Martin Rodriguez Reboredo Reviewed-by: Andreas Hindborg Signed-off-by: Tamir Duberstein Acked-by: Danilo Krummrich 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

rust: kernel: reorder `ForeignOwnable` items

2025-01-13T22:45:54Z

`{into,from}_foreign` before `borrow` is slightly more logical. This removes an inconsistency with `kbox.rs` which already uses this ordering. Reviewed-by: Alice Ryhl Reviewed-by: Andreas Hindborg Signed-off-by: Tamir Duberstein Link: https://lore.kernel.org/r/20241120-borrow-mut-v6-5-80dbadd00951@gmail.com [ Reworded title slightly. - Miguel ] Signed-off-by: Miguel Ojeda

rust: kernel: change `ForeignOwnable` pointer to mut

2025-01-13T22:45:31Z

It is slightly more convenient to operate on mut pointers, and this also properly conveys the desired ownership semantics of the trait. Reviewed-by: Alice Ryhl Reviewed-by: Andreas Hindborg Signed-off-by: Tamir Duberstein Acked-by: Danilo Krummrich Link: https://lore.kernel.org/r/20241120-borrow-mut-v6-4-80dbadd00951@gmail.com [ Reworded title slightly. - Miguel ] Signed-off-by: Miguel Ojeda

rust: arc: split unsafe block, add missing comment

2025-01-13T22:45:31Z

The new SAFETY comment style is taken from existing comments in `deref` and `drop. Reviewed-by: Alice Ryhl Reviewed-by: Andreas Hindborg Signed-off-by: Tamir Duberstein Link: https://lore.kernel.org/r/20241120-borrow-mut-v6-3-80dbadd00951@gmail.com Signed-off-by: Miguel Ojeda

rust: types: avoid `as` casts

2025-01-13T22:45:30Z

Replace `as` casts with `cast{,_mut}` calls which are a bit safer. In one instance, remove an unnecessary `as` cast without replacement. Reviewed-by: Alice Ryhl Reviewed-by: Andreas Hindborg Signed-off-by: Tamir Duberstein Acked-by: Danilo Krummrich Link: https://lore.kernel.org/r/20241120-borrow-mut-v6-2-80dbadd00951@gmail.com Signed-off-by: Miguel Ojeda

rust: arc: use `NonNull::new_unchecked`

2025-01-13T22:45:30Z

There is no need to check (and panic on violations of) the safety requirements on `ForeignOwnable` functions. Avoiding the check is consistent with the implementation of `ForeignOwnable` for `Box`. Reviewed-by: Alice Ryhl Reviewed-by: Andreas Hindborg Signed-off-by: Tamir Duberstein Link: https://lore.kernel.org/r/20241120-borrow-mut-v6-1-80dbadd00951@gmail.com Signed-off-by: Miguel Ojeda

rust: use derive(CoercePointee) on rustc >= 1.84.0

2025-01-13T22:45:30Z

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 Reviewed-by: Fiona Behrens Reviewed-by: Alice Ryhl 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

rust: alloc: add doctest for `ArrayLayout::new()`

2025-01-13T22:45:30Z

Add a rustdoc example and Kunit test to the `ArrayLayout` struct's `ArrayLayout::new()` function. This patch depends on the first patch in this series in order for the KUnit test to compile. Suggested-by: Boqun Feng Link: https://github.com/Rust-for-Linux/linux/issues/1131 Reviewed-by: Danilo Krummrich Signed-off-by: Jimmy Ostler Link: https://lore.kernel.org/r/f1564da5bcaa6be87aee312767a1d1694a03d1b7.1734674670.git.jtostler1@gmail.com [ Added periods to example comments. Reworded title. - Miguel ] Signed-off-by: Miguel Ojeda