pm24.git, branch rust-6.10

rust: alloc: fix dangling pointer in VecExt::reserve()

2024-05-07T22:43:30Z

Currently, a Vec's ptr value, after calling Vec::new(), is initialized to Unique::dangling(). Hence, in VecExt::reserve(), we're passing a dangling pointer (instead of NULL) to krealloc() whenever a new Vec's backing storage is allocated through VecExt extension functions. This only works as long as align_of::(), used by Unique::dangling() to derive the dangling pointer, resolves to a value between 0x0 and ZERO_SIZE_PTR (0x10) and krealloc() hence treats it the same as a NULL pointer however. This isn't a case we should rely on, since there may be types whose alignment may exceed the range still covered by krealloc(), plus other kernel allocators are not as tolerant either. Instead, pass a real NULL pointer to krealloc_aligned() if Vec's capacity is zero. Fixes: 5ab560ce12ed ("rust: alloc: update `VecExt` to take allocation flags") Reviewed-by: Alice Ryhl Reviewed-by: Boqun Feng Reviewed-by: Benno Lossin Signed-off-by: Danilo Krummrich Reviewed-by: Wedson Almeida Filho Link: https://lore.kernel.org/r/20240501134834.22323-1-dakr@redhat.com [ Solved `use` conflict and applied the `if`-instead-of-`match` change discussed in the list. - Miguel ] Signed-off-by: Miguel Ojeda

rust: upgrade to Rust 1.78.0

2024-05-05T18:17:25Z

This is the next upgrade to the Rust toolchain, from 1.77.1 to 1.78.0 (i.e. the latest) [1]. See the upgrade policy [2] and the comments on the first upgrade in commit 3ed03f4da06e ("rust: upgrade to Rust 1.68.2"). It is much smaller than previous upgrades, since the `alloc` fork was dropped in commit 9d0441bab775 ("rust: alloc: remove our fork of the `alloc` crate") [3]. # Unstable features There have been no changes to the set of unstable features used in our own code. Therefore, the only unstable features allowed to be used outside the `kernel` crate is still `new_uninit`. However, since we finally dropped our `alloc` fork [3], all the unstable features used by `alloc` (~30 language ones, ~60 library ones) are not a concern anymore. This reduces the maintenance burden, increases the chances of new compiler versions working without changes and gets us closer to the goal of supporting several compiler versions. It also means that, ignoring non-language/library features, we are currently left with just the few language features needed to implement the kernel `Arc`, the `new_uninit` library feature, the `compiler_builtins` marker and the few `no_*` `cfg`s we pass when compiling `core`/`alloc`. Please see [4] for details. # Required changes ## LLVM's data layout Rust 1.77.0 (i.e. the previous upgrade) introduced a check for matching LLVM data layouts [5]. Then, Rust 1.78.0 upgraded LLVM's bundled major version from 17 to 18 [6], which changed the data layout in x86 [7]. Thus update the data layout in our custom target specification for x86 so that the compiler does not complain about the mismatch: error: data-layout for target `target-5559158138856098584`, `e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128`, differs from LLVM target's `x86_64-linux-gnu` default layout, `e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128` In the future, the goal is to drop the custom target specifications. Meanwhile, if we want to support other LLVM versions used in `rustc` (e.g. for LTO), we will need to add some extra logic (e.g. conditional on LLVM's version, or extracting the data layout from an existing built-in target specification). ## `unused_imports` Rust's `unused_imports` lint covers both unused and redundant imports. Now, in 1.78.0, the lint detects more cases of redundant imports [8]. Thus one of the previous patches cleaned them up. ## Clippy's `new_without_default` Clippy now suggests to implement `Default` even when `new()` is `const`, since `Default::default()` may call `const` functions even if it is not `const` itself [9]. Thus one of the previous patches implemented it. # Other changes in Rust Rust 1.78.0 introduced `feature(asm_goto)` [10] [11]. This feature was discussed in the past [12]. Rust 1.78.0 introduced `feature(const_refs_to_static)` [13] to allow referencing statics in constants and extended `feature(const_mut_refs)` to allow raw mutable pointers in constants. Together, this should cover the kernel's `VTABLE` use case. In fact, the implementation [14] in upstream Rust added a test case for it [15]. Rust 1.78.0 with debug assertions enabled (i.e. `-Cdebug-assertions=y`, kernel's `CONFIG_RUST_DEBUG_ASSERTIONS=y`) now always checks all unsafe preconditions, though without a way to opt-out for particular cases [16]. It would be ideal to have a way to selectively disable certain checks per-call site for this one (i.e. not just per check but for particular instances of a check), even if the vast majority of the checks remain in place [17]. Rust 1.78.0 also improved a couple issues we reported when giving feedback for the new `--check-cfg` feature [18] [19]. # `alloc` upgrade and reviewing As mentioned above, compiler upgrades will not update `alloc` anymore, since we dropped our `alloc` fork [3]. Link: https://github.com/rust-lang/rust/blob/stable/RELEASES.md#version-1780-2024-05-02 [1] Link: https://rust-for-linux.com/rust-version-policy [2] Link: https://lore.kernel.org/rust-for-linux/20240328013603.206764-1-wedsonaf@gmail.com/ [3] Link: https://github.com/Rust-for-Linux/linux/issues/2 [4] Link: https://github.com/rust-lang/rust/pull/120062 [5] Link: https://github.com/rust-lang/rust/pull/120055 [6] Link: https://reviews.llvm.org/D86310 [7] Link: https://github.com/rust-lang/rust/pull/117772 [8] Link: https://github.com/rust-lang/rust-clippy/pull/10903 [9] Link: https://github.com/rust-lang/rust/pull/119365 [10] Link: https://github.com/rust-lang/rust/issues/119364 [11] Link: https://lore.kernel.org/rust-for-linux/ZWipTZysC2YL7qsq@Boquns-Mac-mini.home/ [12] Link: https://github.com/rust-lang/rust/issues/119618 [13] Link: https://github.com/rust-lang/rust/pull/120932 [14] Link: https://github.com/rust-lang/rust/pull/120932/files#diff-e6fc1622c46054cd46b1d225c5386c5554564b3b0fa8a03c2dc2d8627a1079d9 [15] Link: https://github.com/rust-lang/rust/issues/120969 [16] Link: https://github.com/Rust-for-Linux/linux/issues/354 [17] Link: https://github.com/rust-lang/rust/pull/121202 [18] Link: https://github.com/rust-lang/rust/pull/121237 [19] Reviewed-by: Alice Ryhl Link: https://lore.kernel.org/r/20240401212303.537355-4-ojeda@kernel.org [ Added a few more details and links I mentioned in the list. - Miguel ] Signed-off-by: Miguel Ojeda

rust: kernel: remove redundant imports

2024-05-05T17:22:25Z

Rust's `unused_imports` lint covers both unused and redundant imports. In the upcoming 1.78.0, the lint detects more cases of redundant imports [1], e.g.: error: the item `bindings` is imported redundantly --> rust/kernel/print.rs:38:9 | 38 | use crate::bindings; | ^^^^^^^^^^^^^^^ the item `bindings` is already defined by prelude Most cases are `use crate::bindings`, plus a few other items like `Box`. Thus clean them up. Note that, in the `bindings` case, the message "defined by prelude" above means the extern prelude, i.e. the `--extern` flags we pass. Link: https://github.com/rust-lang/rust/pull/117772 [1] Reviewed-by: Alice Ryhl Link: https://lore.kernel.org/r/20240401212303.537355-3-ojeda@kernel.org Signed-off-by: Miguel Ojeda

rust: sync: implement `Default` for `LockClassKey`

2024-05-05T17:22:25Z

In the upcoming Rust 1.78.0, Clippy suggests to implement `Default` even when `new()` is `const`, since `Default::default()` may call `const` functions even if it is not `const` itself [1]: error: you should consider adding a `Default` implementation for `LockClassKey` --> rust/kernel/sync.rs:31:5 | 31 | / pub const fn new() -> Self { 32 | | Self(Opaque::uninit()) 33 | | } | |_____^ Thus implement it. Link: https://github.com/rust-lang/rust-clippy/pull/10903 [1] Reviewed-by: Benno Lossin Reviewed-by: Alice Ryhl Reviewed-by: Boqun Feng Link: https://lore.kernel.org/r/20240401212303.537355-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda

docs: rust: extend abstraction and binding documentation

2024-05-05T17:14:49Z

Add some basics explained by Miguel in [1] to the documentation. And connect it with some hints where this is implemented in the kernel. Link: https://www.linuxfoundation.org/webinars/rust-for-linux-writing-abstractions-and-drivers [1] Cc: Miguel Ojeda Signed-off-by: Dirk Behme Reviewed-by: Benno Lossin Link: https://lore.kernel.org/r/20240418070618.3962736-1-dirk.behme@de.bosch.com [ Reworded first section for better clarity and some minor nits. Changed link into Link tag, use tabs for code block indentation and wrap at 80. - Miguel ] Signed-off-by: Miguel Ojeda

docs: rust: Add instructions for the Rust kselftest

2024-05-05T17:14:42Z

Add section describing how to build and run the Rust kselftest. Signed-off-by: Laura Nao Reviewed-by: Muhammad Usama Anjum Reviewed-by: Valentin Obst Link: https://lore.kernel.org/r/20240405153841.320459-1-laura.nao@collabora.com [ Formatted paths as inline code literals. - Miguel ] Signed-off-by: Miguel Ojeda

rust: remove unneeded `kernel::prelude` imports from doctests

2024-05-05T16:09:04Z

Rust doctests implicitly include `kernel::prelude::*`. Removes explicit `kernel::prelude` imports from doctests. Suggested-by: Miguel Ojeda Link: https://github.com/Rust-for-Linux/linux/issues/1064 Signed-off-by: Nell Shamrell-Harrington Reviewed-by: Benno Lossin Link: https://lore.kernel.org/r/20240411225331.274662-1-nells@linux.microsoft.com [ Add it back for `module_phy_driver`'s example since it is within a `mod`, and thus it cannot be removed. - Miguel ] Signed-off-by: Miguel Ojeda

rust: update `dbg!()` to format column number

2024-05-05T16:09:04Z

In Rust 1.76.0, the `dbg!()` macro was updated to also format the column number. The reason cited was usage of a few characters worth of horizontal space while allowing direct jumps to the source location. [1] Link: https://github.com/rust-lang/rust/pull/114962 [1] Link: https://github.com/Rust-for-Linux/linux/issues/1065 Signed-off-by: Raghav Narang Reviewed-by: Trevor Gross Reviewed-by: Gary Guo Link: https://lore.kernel.org/r/eba70259-9b10-4bf7-ac4f-d7accf6b8891@smtp-relay.sendinblue.com [ Fixed commit author name and removed spurious newline in message. - Miguel ] Signed-off-by: Miguel Ojeda

rust: helpers: Fix grammar in comment

2024-05-05T16:09:04Z

s/directly the bindings/the bindings directly/ Signed-off-by: Thorsten Blum Reviewed-by: Trevor Gross Reviewed-by: Alice Ryhl Link: https://lore.kernel.org/r/20240411205428.537700-1-thorsten.blum@toblux.com Signed-off-by: Miguel Ojeda

rust: init: change the generated name of guard variables

2024-05-05T16:05:00Z

The initializers created by the `[try_][pin_]init!` macros utilize the guard pattern to drop already initialized fields, when initialization fails mid-way. These guards are generated to have the same name as the field that they handle. To prevent namespacing issues [1] when the field name is the same as e.g. a constant name, add `__` as a prefix and `_guard` as the suffix. [ Gary says: "Here's the simplified example: ``` macro_rules! f { () => { let a = 1; let _: u32 = a; } } const a: u64 = 1; fn main() { f!(); } ``` The `a` in `f` have a different hygiene so normally it is scoped to the macro expansion and wouldn't escape. Interestingly a constant is still preferred despite the hygiene so constants escaped into the macro, leading to the error." - Miguel ] Signed-off-by: Benno Lossin Reviewed-by: Boqun Feng Reviewed-by: Alice Ryhl Link: https://lore.kernel.org/rust-for-linux/1e8a2a1f-abbf-44ba-8344-705a9cbb1627@proton.me/ [1] Link: https://lore.kernel.org/r/20240403194321.88716-1-benno.lossin@proton.me [ Added Benno's link and Gary's simplified example. - Miguel ] Signed-off-by: Miguel Ojeda