linux-kernel - Re: [PATCH v6 1/5] rust: add generic static_key

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Message-ID: <CAH5fLgi7dy9PV+YfCJuVoH98M0z2FUnOAjBoFKkqyG8P9iPSEQ@mail.gmail.com>
Date: Fri, 9 Aug 2024 20:21:10 +0200
From: Alice Ryhl <aliceryhl@...gle.com>
To: Gary Guo <gary@...yguo.net>
Cc: Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Peter Zijlstra <peterz@...radead.org>, 
	Josh Poimboeuf <jpoimboe@...nel.org>, Jason Baron <jbaron@...mai.com>, 
	Ard Biesheuvel <ardb@...nel.org>, Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, 
	Wedson Almeida Filho <wedsonaf@...il.com>, Boqun Feng <boqun.feng@...il.com>, 
	Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Benno Lossin <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...sung.com>, 
	linux-trace-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H. Peter Anvin" <hpa@...or.com>, Sean Christopherson <seanjc@...gle.com>, Uros Bizjak <ubizjak@...il.com>, 
	Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>, 
	Oliver Upton <oliver.upton@...ux.dev>, Mark Rutland <mark.rutland@....com>, 
	Ryan Roberts <ryan.roberts@....com>, Fuad Tabba <tabba@...gle.com>, 
	linux-arm-kernel@...ts.infradead.org, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, Anup Patel <apatel@...tanamicro.com>, 
	Andrew Jones <ajones@...tanamicro.com>, Alexandre Ghiti <alexghiti@...osinc.com>, 
	Conor Dooley <conor.dooley@...rochip.com>, Samuel Holland <samuel.holland@...ive.com>, 
	linux-riscv@...ts.infradead.org, Huacai Chen <chenhuacai@...nel.org>, 
	WANG Xuerui <kernel@...0n.name>, Bibo Mao <maobibo@...ngson.cn>, 
	Tiezhu Yang <yangtiezhu@...ngson.cn>, Andrew Morton <akpm@...ux-foundation.org>, 
	Tianrui Zhao <zhaotianrui@...ngson.cn>, loongarch@...ts.linux.dev
Subject: Re: [PATCH v6 1/5] rust: add generic static_key_false

On Fri, Aug 9, 2024 at 8:16 PM Gary Guo <gary@...yguo.net> wrote:
>
> On Thu, 08 Aug 2024 17:23:37 +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.
> >
> > Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
> > ---
> >  rust/bindings/bindings_helper.h       |  1 +
> >  rust/helpers.c                        |  9 +++++++++
> >  rust/kernel/arch_static_branch_asm.rs |  1 +
> >  rust/kernel/jump_label.rs             | 29 +++++++++++++++++++++++++++++
> >  rust/kernel/lib.rs                    |  1 +
> >  5 files changed, 41 insertions(+)
> >
> > diff --git a/rust/kernel/arch_static_branch_asm.rs b/rust/kernel/arch_static_branch_asm.rs
> > new file mode 100644
> > index 000000000000..958f1f130455
> > --- /dev/null
> > +++ b/rust/kernel/arch_static_branch_asm.rs
> > @@ -0,0 +1 @@
> > +::kernel::concat_literals!("1: jmp " "{l_yes}" " # objtool NOPs this \n\t" ".pushsection __jump_table,  \"aw\" \n\t" " " ".balign 8" " " "\n\t" ".long 1b - . \n\t" ".long " "{l_yes}" "- . \n\t" " " ".quad" " " " " "{symb} + {off} + {branch}" " - . \n\t" ".popsection \n\t")
>
>
> I believe this file is included by mistake, given it's added to
> gitignore in patch 5.

We may have to rethink the file extension used here. You have no idea
how many times I've deleted that file from this commit.

Alice