[PATCH v4 2/2] rust: add tracepoint support

[Carlos Llamas]

On Fri, Jun 28, 2024 at 01:23:32PM +0000, Alice Ryhl wrote:
> Make it possible to have Rust code call into tracepoints defined by C
> code. It is still required that the tracepoint is declared in a C
> header, and that this header is included in the input to bindgen.
> 
> Signed-off-by: Alice Ryhl <aliceryhl at google.com>
> ---
>  include/linux/tracepoint.h      | 18 +++++++++++++++-
>  include/trace/define_trace.h    | 12 +++++++++++
>  rust/bindings/bindings_helper.h |  1 +
>  rust/kernel/lib.rs              |  1 +
>  rust/kernel/tracepoint.rs       | 47 +++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 78 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
> index 689b6d71590e..d82af4d77c9f 100644
> --- a/include/linux/tracepoint.h
> +++ b/include/linux/tracepoint.h
> @@ -238,6 +238,20 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
>  #define __DECLARE_TRACE_RCU(name, proto, args, cond)
>  #endif
>  
> +/*
> + * Declare an exported function that Rust code can call to trigger this
> + * tracepoint. This function does not include the static branch; that is done
> + * in Rust to avoid a function call when the tracepoint is disabled.
> + */
> +#define DEFINE_RUST_DO_TRACE(name, proto, args)
> +#define DEFINE_RUST_DO_TRACE_REAL(name, proto, args)			\
nit: IMO using a __* prefix would be a better option to describe the
internal use of the macro instead of the _REAL suffix.

Other than that, this patch looks good to me:

Reviewed-by: Carlos Llamas <cmllamas at google.com>