perf build: Make BUILD_BPF_SKEL default, rename to NO_BPF_SKEL

BPF skeleton support is now key to a number of perf features. Rather
than making it so that BPF support must be enabled for the build, make
this the default and error if the build lacks a clang and libbpf that
are sufficient. To avoid the error and build without BPF skeletons the
NO_BPF_SKEL=1 flag can be used. Add a build-options flag to 'perf
version' to enable detection of the BPF skeleton support and use this
in the offcpu shell test.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andres Freund <andres@anarazel.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Martin Liška <mliska@suse.cz>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Pavithra Gurushankar <gpavithrasha@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Monnet <quentin@isovalent.com>
Cc: Roberto Sassu <roberto.sassu@huawei.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Cc: Tom Rix <trix@redhat.com>
Cc: Yang Jihong <yangjihong1@huawei.com>
Cc: llvm@lists.linux.dev
Link: https://lore.kernel.org/r/20230311065753.3012826-2-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 12 insertions, 7 deletions

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 51a4e26bd030..318af7657225 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -415,6 +415,7 @@ ifdef NO_LIBELF
   NO_LIBUNWIND := 1
   NO_LIBDW_DWARF_UNWIND := 1
   NO_LIBBPF := 1
+  NO_BPF_SKEL := 1
   NO_JVMTI := 1
 else
   ifeq ($(feature-libelf), 0)
@@ -662,18 +663,22 @@ ifndef NO_LIBBPF
     msg := $(warning BPF API too old. Please install recent kernel headers. BPF support in 'perf record' is disabled.)
     NO_LIBBPF := 1
   endif
+else
+  NO_BPF_SKEL := 1
 endif
 
-ifdef BUILD_BPF_SKEL
+ifndef NO_BPF_SKEL
   $(call feature_check,clang-bpf-co-re)
   ifeq ($(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)
+    dummy := $(error: ERROR: BPF skeletons unsupported. clang too old/not installed or build with NO_BPF_SKEL=1.)
+  else
+    ifeq ($(filter -DHAVE_LIBBPF_SUPPORT, $(CFLAGS)),)
+      dummy := $(error: ERROR: BPF skeletons unsupported. BPF skeleton support requires libbpf or build with NO_BPF_SKEL=1.)
+    else
+      $(call detected,CONFIG_PERF_BPF_SKEL)
+      CFLAGS += -DHAVE_BPF_SKEL
+    endif
   endif
-  $(call detected,CONFIG_PERF_BPF_SKEL)
-  CFLAGS += -DHAVE_BPF_SKEL
 endif
 
 dwarf-post-unwind := 1