Revert "perf build: Make BUILD_BPF_SKEL default, rename to NO_BPF_SKEL"

This reverts commit a980755.

We need to better polish building with BPF skels, so revert back to
making it an experimental feature that has to be explicitely enabled
using BUILD_BPF_SKEL=1.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Makefile.config

@@ -415,7 +415,6 @@ 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)
@@ -655,22 +654,18 @@ 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
 
-ifndef NO_BPF_SKEL
+ifdef BUILD_BPF_SKEL
   $(call feature_check,clang-bpf-co-re)
   ifeq ($(feature-clang-bpf-co-re), 0)
-    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
+    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
 
 dwarf-post-unwind := 1

tools/perf/Makefile.perf

@@ -124,7 +124,7 @@ include ../scripts/utilities.mak
 #
 # Define NO_LIBDEBUGINFOD if you do not want support debuginfod
 #
-# Define NO_BPF_SKEL to disable BPF skeletons
+# Define BUILD_BPF_SKEL to enable BPF skeletons
 #
 # Define BUILD_NONDISTRO to enable building an linking against libbfd and
 # libiberty distribution license incompatible libraries.
@@ -1055,7 +1055,7 @@ SKELETONS += $(SKEL_OUT)/kwork_trace.skel.h $(SKEL_OUT)/sample_filter.skel.h
 $(SKEL_TMP_OUT) $(LIBAPI_OUTPUT) $(LIBBPF_OUTPUT) $(LIBPERF_OUTPUT) $(LIBSUBCMD_OUTPUT) $(LIBSYMBOL_OUTPUT):
 	$(Q)$(MKDIR) -p $@
 
-ifndef NO_BPF_SKEL
+ifdef BUILD_BPF_SKEL
 BPFTOOL := $(SKEL_TMP_OUT)/bootstrap/bpftool
 BPF_INCLUDE := -I$(SKEL_TMP_OUT)/.. -I$(LIBBPF_INCLUDE)
 
@@ -1074,11 +1074,11 @@ bpf-skel: $(SKELETONS)
 
 .PRECIOUS: $(SKEL_TMP_OUT)/%.bpf.o
 
-else # NO_BPF_SKEL
+else # BUILD_BPF_SKEL
 
 bpf-skel:
 
-endif # NO_BPF_SKEL
+endif # BUILD_BPF_SKEL
 
 bpf-skel-clean:
 	$(call QUIET_CLEAN, bpf-skel) $(RM) -r $(SKEL_TMP_OUT) $(SKELETONS)

tools/perf/builtin-lock.c

@@ -2387,7 +2387,7 @@ int cmd_lock(int argc, const char **argv)
 
 #ifndef HAVE_BPF_SKEL
 		set_option_nobuild(contention_options, 'b', "use-bpf",
-				   "NO_BPF_SKEL=1", false);
+				   "no BUILD_BPF_SKEL=1", false);
 #endif
 		if (argc) {
 			argc = parse_options(argc, argv, contention_options,

tools/perf/builtin-record.c

@@ -3981,7 +3981,7 @@ int cmd_record(int argc, const char **argv)
 
 #ifndef HAVE_BPF_SKEL
 # define set_nobuild(s, l, m, c) set_option_nobuild(record_options, s, l, m, c)
-	set_nobuild('\0', "off-cpu", "NO_BPF_SKEL=1", true);
+	set_nobuild('\0', "off-cpu", "no BUILD_BPF_SKEL=1", true);
 # undef set_nobuild
 #endif
 

tools/perf/builtin-version.c

@@ -81,7 +81,6 @@ static void library_status(void)
 	STATUS(HAVE_ZSTD_SUPPORT, zstd);
 	STATUS(HAVE_LIBPFM, libpfm4);
 	STATUS(HAVE_LIBTRACEEVENT, libtraceevent);
-	STATUS(HAVE_BPF_SKEL, BPF skeletons);
 }
 
 int cmd_version(int argc, const char **argv)

tools/perf/tests/shell/record_offcpu.sh

@@ -28,7 +28,7 @@ test_offcpu_priv() {
     err=2
     return
   fi
-  if perf version --build-options 2>&1 | grep HAVE_BPF_SKEL | grep -q OFF
+  if perf record --off-cpu -o /dev/null --quiet true 2>&1 | grep BUILD_BPF_SKEL
   then
     echo "off-cpu test [Skipped missing BPF support]"
     err=2