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

[Benno Lossin <benno.lossin@proton.me>]

On 28.06.24 15:23, Alice Ryhl wrote:
> diff --git a/rust/kernel/tracepoint.rs b/rust/kernel/tracepoint.rs
> new file mode 100644
> index 000000000000..1005f09e0330
> --- /dev/null
> +++ b/rust/kernel/tracepoint.rs
> @@ -0,0 +1,47 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +// Copyright (C) 2024 Google LLC.
> +
> +//! Logic for tracepoints.
> +
> +/// Declare the Rust entry point for a tracepoint.
> +#[macro_export]
> +macro_rules! declare_trace {
> +    ($($(#[$attr:meta])* $pub:vis fn $name:ident($($argname:ident : $argtyp:ty),* $(,)?);)*) => {$(
> +        $( #[$attr] )*
> +        #[inline(always)]
> +        $pub unsafe fn $name($($argname : $argtyp),*) {
> +            #[cfg(CONFIG_TRACEPOINTS)]
> +            {
> +                use $crate::bindings::*;

Why is this needed, can't you put this into the invocation of `paste!`?
ie `[< $crate::bindings::__tracepoint_ $name >]`?

> +
> +                // SAFETY: It's always okay to query the static key for a tracepoint.
> +                let should_trace = unsafe {
> +                    $crate::macros::paste! {
> +                        $crate::static_key::static_key_false!(
> +                            [< __tracepoint_ $name >],
> +                            $crate::bindings::tracepoint,
> +                            key
> +                        )
> +                    }
> +                };
> +
> +                if should_trace {
> +                    $crate::macros::paste! {
> +                        // SAFETY: The caller guarantees that it is okay to call this tracepoint.

Can you add this on the docs of `$name`? ie add a Safety section.
The docs should still appear when creating them/when LSPs show them to
you.

---
Cheers,
Benno

> +                        unsafe { [< rust_do_trace_ $name >]($($argname),*) };
> +                    }
> +                }
> +            }
> +
> +            #[cfg(not(CONFIG_TRACEPOINTS))]
> +            {
> +                // If tracepoints are disabled, insert a trivial use of each argument
> +                // to avoid unused argument warnings.
> +                $( let _unused = $argname; )*
> +            }
> +        }
> +    )*}
> +}
> +
> +pub use declare_trace;
> 
> --
> 2.45.2.803.g4e1b14247a-goog
>