On Tue, 02 Dec 2025 19:37:24 +0000
Alice Ryhl <aliceryhl@google.com> wrote:
> This patch series adds __rust_helper to every single rust helper. The
> patches do not depend on each other, so maintainers please go ahead and
> pick up any patches relevant to your subsystem! Or provide your Acked-by
> so that Miguel can pick them up.
>
> These changes were generated by adding __rust_helper and running
> ClangFormat. Unrelated formatting changes were removed manually.
>
> Why is __rust_helper needed?
> ============================
>
> Currently, C helpers cannot be inlined into Rust even when using LTO
> because LLVM detects slightly different options on the codegen units.
>
> * LLVM doesn't want to inline functions compiled with
> `-fno-delete-null-pointer-checks` with code compiled without. The C
> CGUs all have this enabled and Rust CGUs don't. Inlining is okay since
> this is one of the hardening features that does not change the ABI,
> and we shouldn't have null pointer dereferences in these helpers.
>
> * LLVM doesn't want to inline functions with different list of builtins. C
> side has `-fno-builtin-wcslen`; `wcslen` is not a Rust builtin, so
> they should be compatible, but LLVM does not perform inlining due to
> attributes mismatch.
>
> * clang and Rust doesn't have the exact target string. Clang generates
> `+cmov,+cx8,+fxsr` but Rust doesn't enable them (in fact, Rust will
> complain if `-Ctarget-feature=+cmov,+cx8,+fxsr` is used). x86-64
> always enable these features, so they are in fact the same target
> string, but LLVM doesn't understand this and so inlining is inhibited.
> This can be bypassed with `--ignore-tti-inline-compatible`, but this
> is a hidden option.
>
> (This analysis was written by Gary Guo.)
>
> How is this fixed?
> ==================
>
> To fix this we need to add __always_inline to all helpers when compiling
> with LTO. However, it should not be added when running bindgen as
> bindgen will ignore functions marked inline. To achieve this, we are
> using a #define called __rust_helper that is defined differently
> depending on whether bindgen is running or not.
>
> Note that __rust_helper is currently always #defined to nothing.
> Changing it to __always_inline will happen separately in another patch
> series.
>
> Signed-off-by: Alice Ryhl <aliceryhl@google.com>
> ---
> Alice Ryhl (46):
> rust: auxiliary: add __rust_helper to helpers
> rust: barrier: add __rust_helper to helpers
> rust: binder: add __rust_helper to helpers
> rust: bitmap: add __rust_helper to helpers
> rust: bitops: add __rust_helper to helpers
> rust: blk: add __rust_helper to helpers
> rust: bug: add __rust_helper to helpers
> rust: clk: add __rust_helper to helpers
> rust: completion: add __rust_helper to helpers
> rust: cpu: add __rust_helper to helpers
> rust: cpufreq: add __rust_helper to helpers
> rust: cpumask: add __rust_helper to helpers
> rust: cred: add __rust_helper to helpers
> rust: device: add __rust_helper to helpers
> rust: dma: add __rust_helper to helpers
> rust: drm: add __rust_helper to helpers
> rust: err: add __rust_helper to helpers
> rust: fs: add __rust_helper to helpers
> rust: io: add __rust_helper to helpers
> rust: irq: add __rust_helper to helpers
> rust: jump_label: add __rust_helper to helpers
> rust: kunit: add __rust_helper to helpers
> rust: maple_tree: add __rust_helper to helpers
> rust: mm: add __rust_helper to helpers
> rust: of: add __rust_helper to helpers
> rust: pci: add __rust_helper to helpers
> rust: pid_namespace: add __rust_helper to helpers
> rust: platform: add __rust_helper to helpers
> rust: poll: add __rust_helper to helpers
> rust: processor: add __rust_helper to helpers
> rust: property: add __rust_helper to helpers
> rust: rbtree: add __rust_helper to helpers
> rust: rcu: add __rust_helper to helpers
> rust: refcount: add __rust_helper to helpers
> rust: regulator: add __rust_helper to helpers
> rust: scatterlist: add __rust_helper to helpers
> rust: security: add __rust_helper to helpers
> rust: slab: add __rust_helper to helpers
> rust: sync: add __rust_helper to helpers
> rust: task: add __rust_helper to helpers
> rust: time: add __rust_helper to helpers
> rust: uaccess: add __rust_helper to helpers
> rust: usb: add __rust_helper to helpers
> rust: wait: add __rust_helper to helpers
> rust: workqueue: add __rust_helper to helpers
> rust: xarray: add __rust_helper to helpers
Thansk for sending this Alice! With this series in first, my series for
inlining helpers should be much easier to apply.
For the whole series:
Reviewed-by: Gary Guo <gary@garyguo.net>
Best,
Gary
>
> rust/helpers/auxiliary.c | 6 +++--
> rust/helpers/barrier.c | 6 ++---
> rust/helpers/binder.c | 13 ++++-----
> rust/helpers/bitmap.c | 6 +++--
> rust/helpers/bitops.c | 11 +++++---
> rust/helpers/blk.c | 4 +--
> rust/helpers/bug.c | 4 +--
> rust/helpers/build_bug.c | 2 +-
> rust/helpers/clk.c | 24 +++++++++--------
> rust/helpers/completion.c | 2 +-
> rust/helpers/cpu.c | 2 +-
> rust/helpers/cpufreq.c | 3 ++-
> rust/helpers/cpumask.c | 32 +++++++++++++---------
> rust/helpers/cred.c | 4 +--
> rust/helpers/device.c | 16 +++++------
> rust/helpers/dma.c | 15 ++++++-----
> rust/helpers/drm.c | 7 ++---
> rust/helpers/err.c | 6 ++---
> rust/helpers/fs.c | 2 +-
> rust/helpers/io.c | 64 +++++++++++++++++++++++---------------------
> rust/helpers/irq.c | 6 +++--
> rust/helpers/jump_label.c | 2 +-
> rust/helpers/kunit.c | 2 +-
> rust/helpers/maple_tree.c | 3 ++-
> rust/helpers/mm.c | 20 +++++++-------
> rust/helpers/mutex.c | 13 ++++-----
> rust/helpers/of.c | 2 +-
> rust/helpers/page.c | 9 ++++---
> rust/helpers/pci.c | 13 +++++----
> rust/helpers/pid_namespace.c | 8 +++---
> rust/helpers/platform.c | 2 +-
> rust/helpers/poll.c | 5 ++--
> rust/helpers/processor.c | 2 +-
> rust/helpers/property.c | 2 +-
> rust/helpers/rbtree.c | 5 ++--
> rust/helpers/rcu.c | 4 +--
> rust/helpers/refcount.c | 10 +++----
> rust/helpers/regulator.c | 24 ++++++++++-------
> rust/helpers/scatterlist.c | 12 +++++----
> rust/helpers/security.c | 26 ++++++++++--------
> rust/helpers/signal.c | 2 +-
> rust/helpers/slab.c | 14 +++++-----
> rust/helpers/spinlock.c | 13 ++++-----
> rust/helpers/sync.c | 4 +--
> rust/helpers/task.c | 24 ++++++++---------
> rust/helpers/time.c | 12 ++++-----
> rust/helpers/uaccess.c | 8 +++---
> rust/helpers/usb.c | 3 ++-
> rust/helpers/vmalloc.c | 7 ++---
> rust/helpers/wait.c | 2 +-
> rust/helpers/workqueue.c | 8 +++---
> rust/helpers/xarray.c | 10 +++----
> 52 files changed, 280 insertions(+), 226 deletions(-)
> ---
> base-commit: 54e3eae855629702c566bd2e130d9f40e7f35bde
> change-id: 20251202-define-rust-helper-f7b531813007
>
> Best regards,