locking/atomic: scripts: add trivial raw_atomic*_<op>()

Currently a number of arch_atomic*_<op>() functions are optional, and
where an arch does not provide a given arch_atomic*_<op>() we will
define an implementation of arch_atomic*_<op>() in
atomic-arch-fallback.h.

Filling in the missing ops requires special care as we want to select
the optimal definition of each op (e.g. preferentially defining ops in
terms of their relaxed form rather than their fully-ordered form). The
ifdeffery necessary for this requires us to group ordering variants
together, which can be a bit painful to read, and is painful for
kerneldoc generation.

It would be easier to handle this if we generated ops into a separate
namespace, as this would remove the need to take special care with the
ifdeffery, and allow each ordering variant to be generated separately.

This patch adds a new set of raw_atomic_<op>() definitions, which are
currently trivial wrappers of their arch_atomic_<op>() equivalent. This
will allow us to move treewide users of arch_atomic_<op>() over to raw
atomic op before we rework the fallback generation to generate
raw_atomic_<op> directly.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230605070124.3741859-18-mark.rutland@arm.com

include/linux/atomic.h

@@ -79,6 +79,7 @@
 
 #include <linux/atomic/atomic-arch-fallback.h>
 #include <linux/atomic/atomic-long.h>
+#include <linux/atomic/atomic-raw.h>
 #include <linux/atomic/atomic-instrumented.h>
 
 #endif /* _LINUX_ATOMIC_H */

scripts/atomic/gen-atomic-instrumented.sh

@@ -73,7 +73,7 @@ static __always_inline ${ret}
 ${atomicname}(${params})
 {
 ${checks}
-	${retstmt}arch_${atomicname}(${args});
+	${retstmt}raw_${atomicname}(${args});
 }
 EOF
 
@@ -105,7 +105,7 @@ EOF
 cat <<EOF
 	instrument_atomic_read_write(__ai_ptr, sizeof(*__ai_ptr)); \\
 	instrument_read_write(__ai_oldp, sizeof(*__ai_oldp)); \\
-	arch_${xchg}${order}(__ai_ptr, __ai_oldp, __VA_ARGS__); \\
+	raw_${xchg}${order}(__ai_ptr, __ai_oldp, __VA_ARGS__); \\
 })
 EOF
 
@@ -119,7 +119,7 @@ EOF
 [ -n "$kcsan_barrier" ] && printf "\t${kcsan_barrier}; \\\\\n"
 cat <<EOF
 	instrument_atomic_read_write(__ai_ptr, sizeof(*__ai_ptr)); \\
-	arch_${xchg}${order}(__ai_ptr, __VA_ARGS__); \\
+	raw_${xchg}${order}(__ai_ptr, __VA_ARGS__); \\
 })
 EOF
 
@@ -133,15 +133,10 @@ cat << EOF
 // DO NOT MODIFY THIS FILE DIRECTLY
 
 /*
- * This file provides wrappers with KASAN instrumentation for atomic operations.
- * To use this functionality an arch's atomic.h file needs to define all
- * atomic operations with arch_ prefix (e.g. arch_atomic_read()) and include
- * this file at the end. This file provides atomic_read() that forwards to
- * arch_atomic_read() for actual atomic operation.
- * Note: if an arch atomic operation is implemented by means of other atomic
- * operations (e.g. atomic_read()/atomic_cmpxchg() loop), then it needs to use
- * arch_ variants (i.e. arch_atomic_read()/arch_atomic_cmpxchg()) to avoid
- * double instrumentation.
+ * This file provoides atomic operations with explicit instrumentation (e.g.
+ * KASAN, KCSAN), which should be used unless it is necessary to avoid
+ * instrumentation. Where it is necessary to aovid instrumenation, the
+ * raw_atomic*() operations should be used.
  */
 #ifndef _LINUX_ATOMIC_INSTRUMENTED_H
 #define _LINUX_ATOMIC_INSTRUMENTED_H

scripts/atomic/gen-atomic-raw.sh

@@ -0,0 +1,84 @@
+#!/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
+static __always_inline ${ret}
+raw_${atomicname}(${params})
+{
+	${retstmt}arch_${atomicname}(${args});
+}
+
+EOF
+}
+
+gen_xchg()
+{
+	local xchg="$1"; shift
+	local order="$1"; shift
+
+cat <<EOF
+#define raw_${xchg}${order}(...) \\
+	arch_${xchg}${order}(__VA_ARGS__)
+EOF
+}
+
+cat << EOF
+// SPDX-License-Identifier: GPL-2.0
+
+// Generated by $0
+// DO NOT MODIFY THIS FILE DIRECTLY
+
+#ifndef _LINUX_ATOMIC_RAW_H
+#define _LINUX_ATOMIC_RAW_H
+
+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
+
+grep '^[a-z]' "$1" | while read name meta args; do
+	gen_proto "${meta}" "${name}" "atomic_long" "long" ${args}
+done
+
+for xchg in "xchg" "cmpxchg" "cmpxchg64" "cmpxchg128" "try_cmpxchg" "try_cmpxchg64" "try_cmpxchg128"; do
+	for order in "" "_acquire" "_release" "_relaxed"; do
+		gen_xchg "${xchg}" "${order}"
+		printf "\n"
+	done
+done
+
+for xchg in "cmpxchg_local" "cmpxchg64_local" "cmpxchg128_local" "sync_cmpxchg" "try_cmpxchg_local" "try_cmpxchg64_local" "try_cmpxchg128_local"; do
+	gen_xchg "${xchg}" ""
+	printf "\n"
+done
+
+cat <<EOF
+#endif /* _LINUX_ATOMIC_RAW_H */
+EOF

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-atomic-raw.sh               linux/atomic/atomic-raw.h
 EOF
 while read script header args; do
 	/bin/sh ${ATOMICDIR}/${script} ${ATOMICTBL} ${args} > ${LINUXDIR}/include/${header}