perf build: Error for BPF skeletons without LIBBPF

LIBBPF requires LIBELF so doing "make BUILD_BPF_SKEL=1 NO_LIBELF=1"
fails with compiler errors about missing declarations. Similar could
happen if libbpf feature detection fails.

Prefer to error when BUILD_BPF_SKEL is enabled but LIBBPF isn't.

Signed-off-by: Ian Rogers <[email protected]>
Acked-by: Jiri Olsa <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Daniel Borkmann <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: John Fastabend <[email protected]>
Cc: KP Singh <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Martin KaFai Lau <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Song Liu <[email protected]>
Cc: Yonghong Song <[email protected]>
Cc: [email protected]
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

1 files changed, 3 insertions, 0 deletions

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index c38423807d01..e0304e70f182 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -671,6 +671,9 @@ ifdef BUILD_BPF_SKEL
   ifeq ($(feature-clang-bpf-co-re), 0)
     dummy := $(error Error: clang too old/not installed. Please install recent clang to build with BUILD_BPF_SKEL)
   endif
+  ifeq ($(filter -DHAVE_LIBBPF_SUPPORT, $(CFLAGS)),)
+    dummy := $(error Error: BPF skeleton support requires libbpf)
+  endif
   $(call detected,CONFIG_PERF_BPF_SKEL)
   CFLAGS += -DHAVE_BPF_SKEL
 endif