rust: Introduce atomic API helpers

In order to support LKMM atomics in Rust, add rust_helper_* for atomic
APIs. These helpers ensure the implementation of LKMM atomics in Rust is
the same as in C. This could save the maintenance burden of having two
similar atomic implementations in asm.

Originally-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/all/20250719030827.61357-2-boqun.feng@gmail.com/

2 files changed, 68 insertions, 0 deletions

diff --git a/scripts/atomic/gen-atomics.sh b/scripts/atomic/gen-atomics.sh
index 5b98a8307693..02508d0d6fe4 100755
--- a/scripts/atomic/gen-atomics.sh
+++ b/scripts/atomic/gen-atomics.sh
@@ -11,6 +11,7 @@ cat <<EOF |
 gen-atomic-instrumented.sh      linux/atomic/atomic-instrumented.h
 gen-atomic-long.sh              linux/atomic/atomic-long.h
 gen-atomic-fallback.sh          linux/atomic/atomic-arch-fallback.h
+gen-rust-atomic-helpers.sh      ../rust/helpers/atomic.c
 EOF
 while read script header args; do
 	/bin/sh ${ATOMICDIR}/${script} ${ATOMICTBL} ${args} > ${LINUXDIR}/include/${header}
diff --git a/scripts/atomic/gen-rust-atomic-helpers.sh b/scripts/atomic/gen-rust-atomic-helpers.sh
new file mode 100755
index 000000000000..45b1e100ed7c
--- /dev/null
+++ b/scripts/atomic/gen-rust-atomic-helpers.sh
@@ -0,0 +1,67 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+ATOMICDIR=$(dirname $0)
+
+. ${ATOMICDIR}/atomic-tbl.sh
+
+#gen_proto_order_variant(meta, pfx, name, sfx, order, atomic, int, arg...)
+gen_proto_order_variant()
+{
+	local meta="$1"; shift
+	local pfx="$1"; shift
+	local name="$1"; shift
+	local sfx="$1"; shift
+	local order="$1"; shift
+	local atomic="$1"; shift
+	local int="$1"; shift
+
+	local atomicname="${atomic}_${pfx}${name}${sfx}${order}"
+
+	local ret="$(gen_ret_type "${meta}" "${int}")"
+	local params="$(gen_params "${int}" "${atomic}" "$@")"
+	local args="$(gen_args "$@")"
+	local retstmt="$(gen_ret_stmt "${meta}")"
+
+cat <<EOF
+__rust_helper ${ret}
+rust_helper_${atomicname}(${params})
+{
+	${retstmt}${atomicname}(${args});
+}
+
+EOF
+}
+
+cat << EOF
+// SPDX-License-Identifier: GPL-2.0
+
+// Generated by $0
+// DO NOT MODIFY THIS FILE DIRECTLY
+
+/*
+ * This file provides helpers for the various atomic functions for Rust.
+ */
+#ifndef _RUST_ATOMIC_API_H
+#define _RUST_ATOMIC_API_H
+
+#include <linux/atomic.h>
+
+// TODO: Remove this after INLINE_HELPERS support is added.
+#ifndef __rust_helper
+#define __rust_helper
+#endif
+
+EOF
+
+grep '^[a-z]' "$1" | while read name meta args; do
+	gen_proto "${meta}" "${name}" "atomic" "int" ${args}
+done
+
+grep '^[a-z]' "$1" | while read name meta args; do
+	gen_proto "${meta}" "${name}" "atomic64" "s64" ${args}
+done
+
+cat <<EOF
+#endif /* _RUST_ATOMIC_API_H */
+EOF