linux-kernel - Re: [PATCH v9 1/5] rust: add generic static_key

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Message-ID: <20241001101201.7a43726d@gandalf.local.home>
Date: Tue, 1 Oct 2024 10:12:01 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Peter Zijlstra <peterz@...radead.org>,
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Subject: Re: [PATCH v9 1/5] rust: add generic static_key_false

On Tue, 01 Oct 2024 13:29:58 +0000
Alice Ryhl <aliceryhl@...gle.com> wrote:

> Add just enough support for static key so that we can use it from
> tracepoints. Tracepoints rely on `static_key_false` even though it is
> deprecated, so we add the same functionality to Rust.
> 
> This patch only provides a generic implementation without code patching
> (matching the one used when CONFIG_JUMP_LABEL is disabled). Later
> patches add support for inline asm implementations that use runtime
> patching.
> 
> When CONFIG_JUMP_LABEL is unset, `static_key_count` is a static inline
> function, so a Rust helper is defined for `static_key_count` in this
> case. If Rust is compiled with LTO, this call should get inlined. The
> helper can be eliminated once we have the necessary inline asm to make
> atomic operations from Rust.
> 
> Reviewed-by: Boqun Feng <boqun.feng@...il.com>
> Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
> ---
>  rust/bindings/bindings_helper.h |  1 +
>  rust/helpers/helpers.c          |  1 +
>  rust/helpers/jump_label.c       | 15 +++++++++++++++
>  rust/kernel/jump_label.rs       | 29 +++++++++++++++++++++++++++++
>  rust/kernel/lib.rs              |  1 +
>  5 files changed, 47 insertions(+)
> 
> diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
> index ae82e9c941af..e0846e7e93e6 100644
> --- a/rust/bindings/bindings_helper.h
> +++ b/rust/bindings/bindings_helper.h
> @@ -14,6 +14,7 @@
>  #include <linux/ethtool.h>
>  #include <linux/firmware.h>
>  #include <linux/jiffies.h>
> +#include <linux/jump_label.h>
>  #include <linux/mdio.h>
>  #include <linux/phy.h>
>  #include <linux/refcount.h>
> diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
> index 30f40149f3a9..17e1b60d178f 100644
> --- a/rust/helpers/helpers.c
> +++ b/rust/helpers/helpers.c
> @@ -12,6 +12,7 @@
>  #include "build_assert.c"
>  #include "build_bug.c"
>  #include "err.c"
> +#include "jump_label.c"
>  #include "kunit.c"
>  #include "mutex.c"
>  #include "page.c"
> diff --git a/rust/helpers/jump_label.c b/rust/helpers/jump_label.c
> new file mode 100644
> index 000000000000..0e9ed15903f6
> --- /dev/null
> +++ b/rust/helpers/jump_label.c
> @@ -0,0 +1,15 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Copyright (C) 2024 Google LLC.
> + */
> +
> +#include <linux/jump_label.h>
> + 

Nit, the above line has a spurious space.

-- Steve

> +#ifndef CONFIG_JUMP_LABEL
> +int rust_helper_static_key_count(struct static_key *key)
> +{
> +       return static_key_count(key);
> +}
> +EXPORT_SYMBOL_GPL(rust_helper_static_key_count);
> +#endif
> diff --git a/rust/kernel/jump_label.rs b/rust/kernel/jump_label.rs
> new file mode 100644