[PATCH v6 1/5] rust: add generic static_key_false

[Alice Ryhl]

On Fri, Aug 9, 2024 at 8:16 PM Gary Guo <gary at garyguo.net> wrote:
>
> On Thu, 08 Aug 2024 17:23:37 +0000
> Alice Ryhl <aliceryhl at google.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 at google.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