kbuild: Add CONFIG_PAHOLE_VERSION

There are a few different places where pahole's version is turned into a
three digit form with the exact same command. Move this command into
scripts/pahole-version.sh to reduce the amount of duplication across the
tree.

Create CONFIG_PAHOLE_VERSION so the version code can be used in Kconfig
to enable and disable configuration options based on the pahole version,
which is already done in a couple of places.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220201205624.652313-3-nathan@kernel.org

MAINTAINERS

@@ -3524,6 +3524,7 @@ F:	net/sched/cls_bpf.c
 F:	samples/bpf/
 F:	scripts/bpf_doc.py
 F:	scripts/pahole-flags.sh
+F:	scripts/pahole-version.sh
 F:	tools/bpf/
 F:	tools/lib/bpf/
 F:	tools/testing/selftests/bpf/

init/Kconfig

@@ -86,6 +86,10 @@ config CC_HAS_ASM_INLINE
 config CC_HAS_NO_PROFILE_FN_ATTR
 	def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
 
+config PAHOLE_VERSION
+	int
+	default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE))
+
 config CONSTRUCTORS
 	bool
 

scripts/pahole-version.sh

@@ -0,0 +1,13 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# Usage: $ ./pahole-version.sh pahole
+#
+# Prints pahole's version in a 3-digit form, such as 119 for v1.19.
+
+if [ ! -x "$(command -v "$@")" ]; then
+	echo 0
+	exit 1
+fi
+
+"$@" --version | sed -E 's/v([0-9]+)\.([0-9]+)/\1\2/'