[RFC 2/2] perf build: Prefer kernel source headers for BPF skeletons

[hupu <hupu.gm@gmail.com>]

When building eBPF skeletons with Clang, prefer header files provided by
the kernel source tree over headers installed on the host system.

While host-installed UAPI headers can be sufficient today, they are
tightly coupled to the host environment and may diverge from the target
kernel version over time as the kernel evolves. Relying on kernel source
headers helps ensure that the headers used during the build remain
consistent with the target kernel version and reduces dependence on the
host build environment.

This change adds the kernel source UAPI and generated header paths to
the BPF include list and places them before the system include paths,
while still keeping host headers (CLANG_SYS_INCLUDES) as a fallback.

Signed-off-by: hupu <hupu.gm@gmail.com>
---
 tools/perf/Makefile.perf | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index 8b8647fd4f41..57c73ab98703 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -1203,7 +1203,13 @@ endif
 
 CLANG_OPTIONS = -Wall
 CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG),$(CLANG_TARGET_ARCH))
-BPF_INCLUDE := -I$(SKEL_TMP_OUT)/.. -I$(LIBBPF_INCLUDE) $(CLANG_SYS_INCLUDES)
+
+KHDR_INCLUDES := -I$(abspath $(OUTPUT)../../usr/include) \
+-I$(abspath $(OUTPUT)../../arch/$(SRCARCH)/include/generated/uapi) \
+-I$(abspath $(OUTPUT)../../arch/$(SRCARCH)/include/uapi)
+
+BPF_INCLUDE := -I$(SKEL_TMP_OUT)/.. -I$(LIBBPF_INCLUDE) \
+		$(KHDR_INCLUDES) $(CLANG_SYS_INCLUDES)
 TOOLS_UAPI_INCLUDE := -I$(srctree)/tools/include/uapi
 
 ifneq ($(WERROR),0)
-- 
2.43.0