[v12,0/5] Tracepoints and static branch in Rust

Message

Alice Ryhl Oct. 30, 2024, 4:04 p.m. UTC

An important part of a production ready Linux kernel driver is
tracepoints. So to write production ready Linux kernel drivers in Rust,
we must be able to call tracepoints from Rust code. This patch series
adds support for calling tracepoints declared in C from Rust.

This series includes a patch that adds a user of tracepoints to the
rust_print sample. Please see that sample for details on what is needed
to use this feature in Rust code.

This is intended for use in the Rust Binder driver, which was originally
sent as an RFC [1]. The RFC did not include tracepoint support, but you
can see how it will be used in Rust Binder at [2]. The author has
verified that the tracepoint support works on Android devices.

This implementation implements support for static keys in Rust so that
the actual static branch happens in the Rust object file. However, the
__DO_TRACE body remains in C code. See v1 for an implementation where
__DO_TRACE is also implemented in Rust.

Based on top of commit eb887c4567d1 ("tracing: Use atomic64_inc_return()
in trace_clock_counter()") from trace/for-next, which is in turn based
on top of v6.12-rc2.

The sample added in this series is affected by [3], so be aware that
some bindgen/libclang combinations may fail to build the sample. This
isn't something that this patch series needs to fix, though.

Link: https://lore.kernel.org/rust-for-linux/[e-mail]/ [1]
Link: https://r.android.com/3119993 [2]
Link: https://lore.kernel.org/all/[e-mail]/ [3]
Signed-off-by: Alice Ryhl <[e-mail]>
---
Changes in v12:
- Replace `ifneq ($(CONFIG_JUMP_LABEL),)` with `ifdef CONFIG_JUMP_LABEL`.
- Expand x86 asm to 32-bit for future-compat.
- Add note to coverletter about libclang issue.
- Link to v11: https://lore.kernel.org/r/[e-mail]

Changes in v11:
- Fix build failure with CONFIG_JUMP_LABEL disabled.
- Remove CONFIG_HAVE_JUMP_LABEL_HACK duplication.
- Remove explicit export of rust_helper_static_key_count.
- Add Gary's Reviewed-by to first patch.
- Link to v10: https://lore.kernel.org/r/[e-mail]

Changes in v10:
- Rebase on trace/for-next.
- Use static_branch_unlikely as of [PATCH] tracepoints: Use new static branch API.
- Update second patch as of [PATCH] tracing: Declare system call tracepoints with TRACE_EVENT_SYSCALL.
- Link to v9: https://lore.kernel.org/r/[e-mail]

Changes in v9:
- Rebase on v6.12-rc1.
- Add some Reviewed-by tags from Boqun.
- Link to v8: https://lore.kernel.org/r/[e-mail]

Changes in v8:
- Use OBJTREE instead of SRCTREE for temporary asm file.
- Adjust comments on `asm!` wrapper to be less confusing.
- Include resolution of conflict with helpers splitting.
- Link to v7: https://lore.kernel.org/r/[e-mail]

Changes in v7:
- Fix spurious file included in first patch.
- Fix issue with riscv asm.
- Fix tags on fourth patch to match fifth patch.
- Add Reviewed-by/Acked-by tags where appropriate.
- Link to v6: https://lore.kernel.org/r/[e-mail]

Changes in v6:
- Add support for !CONFIG_JUMP_LABEL.
- Add tracepoint to rust_print sample.
- Deduplicate inline asm.
- Require unsafe inside `declare_trace!`.
- Fix bug on x86 due to use of intel syntax.
- Link to v5: https://lore.kernel.org/r/[e-mail]

Changes in v5:
- Update first patch regarding inline asm duplication.
- Add __rust_do_trace helper to support conditions.
- Rename DEFINE_RUST_DO_TRACE_REAL to __DEFINE_RUST_DO_TRACE.
- Get rid of glob-import in tracepoint macro.
- Address safety requirements on tracepoints in docs.
- Link to v4: https://lore.kernel.org/rust-for-linux/[e-mail]

Changes in v4:
- Move arch-specific code into rust/kernel/arch.
- Restore DEFINE_RUST_DO_TRACE at end of define_trace.h
- Link to v3: https://lore.kernel.org/r/[e-mail]

Changes in v3:
- Support for Rust static_key on loongarch64 and riscv64.
- Avoid failing compilation on architectures that are missing Rust
  static_key support when the archtectures does not actually use it.
- Link to v2: https://lore.kernel.org/r/[e-mail]

Changes in v2:
- Call into C code for __DO_TRACE.
- Drop static_call patch, as it is no longer needed.
- Link to v1: https://lore.kernel.org/r/[e-mail]

---
Alice Ryhl (5):
      rust: add static_branch_unlikely for static_key_false
      rust: add tracepoint support
      rust: samples: add tracepoint to Rust sample
      jump_label: adjust inline asm to be consistent
      rust: add arch_static_branch

 MAINTAINERS                             |  1 +
 arch/arm/include/asm/jump_label.h       | 14 ++++---
 arch/arm64/include/asm/jump_label.h     | 20 +++++----
 arch/loongarch/include/asm/jump_label.h | 16 ++++---
 arch/riscv/include/asm/jump_label.h     | 50 ++++++++++++----------
 arch/x86/include/asm/jump_label.h       | 35 ++++++----------
 include/linux/tracepoint.h              | 28 ++++++++++++-
 include/trace/define_trace.h            | 12 ++++++
 include/trace/events/rust_sample.h      | 31 ++++++++++++++
 rust/Makefile                           |  6 +++
 rust/bindings/bindings_helper.h         |  3 ++
 rust/helpers/helpers.c                  |  1 +
 rust/helpers/jump_label.c               | 14 +++++++
 rust/kernel/.gitignore                  |  3 ++
 rust/kernel/arch_static_branch_asm.rs.S |  7 ++++
 rust/kernel/jump_label.rs               | 74 +++++++++++++++++++++++++++++++++
 rust/kernel/lib.rs                      | 37 +++++++++++++++++
 rust/kernel/tracepoint.rs               | 49 ++++++++++++++++++++++
 samples/rust/Makefile                   |  3 +-
 samples/rust/rust_print.rs              | 18 ++++++++
 samples/rust/rust_print_events.c        |  8 ++++
 scripts/Makefile.build                  |  9 +++-
 22 files changed, 374 insertions(+), 65 deletions(-)
---
base-commit: eb887c4567d1b0e7684c026fe7df44afa96589e6
change-id: 20240606-tracepoint-31e15b90e471

Best regards,