linux-kernel - [PATCH] perf build: Support passing extra Clang options via EXTRA_BPF

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Message-ID: <20251020024049.6877-1-hupu.gm@gmail.com>
Date: Mon, 20 Oct 2025 10:40:49 +0800
From: hupu <hupu.gm@...il.com>
To: hupu.gm@...il.com
Cc: acme@...nel.org,
	adrian.hunter@...el.com,
	alexander.shishkin@...ux.intel.com,
	irogers@...gle.com,
	jolsa@...nel.org,
	justinstitt@...gle.com,
	leo.yan@....com,
	linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org,
	mark.rutland@....com,
	mingo@...hat.com,
	morbo@...gle.com,
	namhyung@...nel.org,
	nathan@...nel.org,
	nick.desaulniers+lkml@...il.com,
	peterz@...radead.org
Subject: [PATCH] perf build: Support passing extra Clang options via EXTRA_BPF_FLAGS

When cross-compiling perf with BPF enabled, Clang is invoked during the
build. Some cross-compilation environments require additional compiler
options, such as `--sysroot` or custom include paths.

This patch introduces a new Make variable, `EXTRA_BPF_FLAGS`. During BPF
skeleton builds, it appends user-provided options to `CLANG_OPTIONS`,
allowing extra Clang flags to be set without modifying Makefile.perf
directly.

Example usage:
    EXTRA_BPF_FLAGS="--sysroot=$SYSROOT"
    make perf ARCH="$ARCH" EXTRA_BPF_FLAGS="$EXTRA_BPF_FLAGS"

Change history:
  v2:
    - Rename EXTRA_CLANG_FLAGS to EXTRA_BPF_FLAGS
    - Update commit message
  v1:
    - Introduce EXTRA_CLANG_FLAGS to allow passing extra Clang options

Signed-off-by: hupu <hupu.gm@...il.com>
---
 tools/perf/Makefile.perf | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index 47c906b807ef..f1f2efdbab8c 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -1249,6 +1249,11 @@ else
 	$(Q)cp "$(VMLINUX_H)" $@
 endif
 
+# Allow users to specify additional Clang options (e.g. --sysroot)
+# when cross-compiling BPF skeletons, enabling more flexible
+# build configurations.
+CLANG_OPTIONS += $(EXTRA_BPF_FLAGS)
+
 $(SKEL_TMP_OUT)/%.bpf.o: $(OUTPUT)PERF-VERSION-FILE util/bpf_skel/perf_version.h | $(SKEL_TMP_OUT)
 $(SKEL_TMP_OUT)/%.bpf.o: util/bpf_skel/%.bpf.c $(LIBBPF) $(SKEL_OUT)/vmlinux.h
 	$(QUIET_CLANG)$(CLANG) -g -O2 -fno-stack-protector --target=bpf \
-- 
2.43.0