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This is the second upgrade to the Rust toolchain, from 1.71.1 to 1.72.0 (i.e. the latest) [1]. See the upgrade policy [2] and the comments on the first upgrade in commit 3ed03f4 ("rust: upgrade to Rust 1.68.2"). # Unstable features No unstable features (that we use) were stabilized. Therefore, the only unstable feature allowed to be used outside the `kernel` crate is still `new_uninit`, though other code to be upstreamed may increase the list. Please see [3] for details. # Other improvements Previously, the compiler could incorrectly generate a `.eh_frame` section under `-Cpanic=abort`. We were hitting this bug in our old `rust` branch [4]. Gary fixed the issue in Rust 1.72.0 [5]. # Required changes For the upgrade, the following changes are required: - A call to `Box::from_raw` in `rust/kernel/sync/arc.rs` now requires an explicit `drop()` call. See previous patch for details. # `alloc` upgrade and reviewing The vast majority of changes are due to our `alloc` fork being upgraded at once. There are two kinds of changes to be aware of: the ones coming from upstream, which we should follow as closely as possible, and the updates needed in our added fallible APIs to keep them matching the newer infallible APIs coming from upstream. Instead of taking a look at the diff of this patch, an alternative approach is reviewing a diff of the changes between upstream `alloc` and the kernel's. This allows to easily inspect the kernel additions only, especially to check if the fallible methods we already have still match the infallible ones in the new version coming from upstream. Another approach is reviewing the changes introduced in the additions in the kernel fork between the two versions. This is useful to spot potentially unintended changes to our additions. To apply these approaches, one may follow steps similar to the following to generate a pair of patches that show the differences between upstream Rust and the kernel (for the subset of `alloc` we use) before and after applying this patch: # Get the difference with respect to the old version. git -C rust checkout $(linux/scripts/min-tool-version.sh rustc) git -C linux ls-tree -r --name-only HEAD -- rust/alloc | cut -d/ -f3- | grep -Fv README.md | xargs -IPATH cp rust/library/alloc/src/PATH linux/rust/alloc/PATH git -C linux diff --patch-with-stat --summary -R > old.patch git -C linux restore rust/alloc # Apply this patch. git -C linux am rust-upgrade.patch # Get the difference with respect to the new version. git -C rust checkout $(linux/scripts/min-tool-version.sh rustc) git -C linux ls-tree -r --name-only HEAD -- rust/alloc | cut -d/ -f3- | grep -Fv README.md | xargs -IPATH cp rust/library/alloc/src/PATH linux/rust/alloc/PATH git -C linux diff --patch-with-stat --summary -R > new.patch git -C linux restore rust/alloc Now one may check the `new.patch` to take a look at the additions (first approach) or at the difference between those two patches (second approach). For the latter, a side-by-side tool is recommended. Link: https://github.com/rust-lang/rust/blob/stable/RELEASES.md#version-1720-2023-08-24 [1] Link: https://rust-for-linux.com/rust-version-policy [2] Link: Rust-for-Linux#2 [3] Closes: Rust-for-Linux#1012 [4] Link: rust-lang/rust#112403 [5] Signed-off-by: Miguel Ojeda <[email protected]>
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