Messages in this thread | | | From | Trevor Gross <> | Date | Wed, 2 Aug 2023 03:43:16 -0400 | Subject | Re: [PATCH 1/2] rust: upgrade to Rust 1.71.0 |
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On Sat, Jul 29, 2023 at 6:05 PM Miguel Ojeda <ojeda@kernel.org> wrote: > > This is the second upgrade to the Rust toolchain, from 1.68.2 to 1.71.0 > (i.e. the latest). > > See the upgrade policy [1] and the comments on the first upgrade in > commit 3ed03f4da06e ("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 [2] for details. > > # Required changes > > For the upgrade, this patch requires the following changes: > > - Removal of the `__rust_*` allocator functions, together with > the addition of the `__rust_no_alloc_shim_is_unstable` static. > See [3] for details. > > - Some more compiler builtins added due to `<f{32,64}>::midpoint()` > that got added in Rust 1.71 [4]. > > # `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://rust-for-linux.com/rust-version-policy [1] > Link: https://github.com/Rust-for-Linux/linux/issues/2 [2] > Link: https://github.com/rust-lang/rust/pull/86844 [3] > Link: https://github.com/rust-lang/rust/pull/92048 [4] > Signed-off-by: Miguel Ojeda <ojeda@kernel.org> > [...]
Reviewed-by: Trevor Gross <tmgross@umich.edu>
A few highlights since 1.68.2 that may eventually be of use:
- `CStr::is_empty` and `CStr::from_bytes_until_nul` help smooth FFI a bit - `NonNull::slice_from_raw_parts` for slice pointers - `AtomicX::as_ptr` makes interop with C more clear (doesn't seem like we use these types anywhere yet) - const `ptr::read` and `ptr::read_unaligned` - `{Option, Result}::is_some_and` - `core::cell::OnceCell` one-time initialization - `repr(C)` enums now use `c_int` rather than always `i32` (no difference for currently supported targets)
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