selftests/bpf: Fix silent Makefile output

99aaceb ("selftests: do not use .ONESHELL") removed .ONESHELL, which
changes how Makefile "silences" multi-command target recipes. selftests/bpf's
Makefile relied (a somewhat unknowingly) on .ONESHELL behavior of silencing
all commands within the recipe if the first command contains @ symbol.
Removing .ONESHELL exposed this hack.

This patch fixes the issue by explicitly silencing each command with $(Q).

Also explicitly define fallback rule for building *.o from *.c, instead of
relying on non-silent inherited rule. This was causing a non-silent output for
bench.o object file.

Fixes: 92f7440 ("selftests/bpf: More succinct Makefile output")
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200807033058.848677-1-andriin@fb.com

tools/testing/selftests/bpf/Makefile

@@ -102,7 +102,7 @@ endif
 OVERRIDE_TARGETS := 1
 override define CLEAN
 	$(call msg,CLEAN)
-	$(RM) -r $(TEST_GEN_PROGS) $(TEST_GEN_PROGS_EXTENDED) $(TEST_GEN_FILES) $(EXTRA_CLEAN)
+	$(Q)$(RM) -r $(TEST_GEN_PROGS) $(TEST_GEN_PROGS_EXTENDED) $(TEST_GEN_FILES) $(EXTRA_CLEAN)
 endef
 
 include ../lib.mk
@@ -123,17 +123,21 @@ $(notdir $(TEST_GEN_PROGS)						\
 	 $(TEST_GEN_PROGS_EXTENDED)					\
 	 $(TEST_CUSTOM_PROGS)): %: $(OUTPUT)/% ;
 
+$(OUTPUT)/%.o: %.c
+	$(call msg,CC,,$@)
+	$(Q)$(CC) $(CFLAGS) -c $(filter %.c,$^) $(LDLIBS) -o $@
+
 $(OUTPUT)/%:%.c
 	$(call msg,BINARY,,$@)
-	$(LINK.c) $^ $(LDLIBS) -o $@
+	$(Q)$(LINK.c) $^ $(LDLIBS) -o $@
 
 $(OUTPUT)/urandom_read: urandom_read.c
 	$(call msg,BINARY,,$@)
-	$(CC) $(LDFLAGS) -o $@ $< $(LDLIBS) -Wl,--build-id
+	$(Q)$(CC) $(LDFLAGS) -o $@ $< $(LDLIBS) -Wl,--build-id
 
 $(OUTPUT)/test_stub.o: test_stub.c $(BPFOBJ)
 	$(call msg,CC,,$@)
-	$(CC) -c $(CFLAGS) -o $@ $<
+	$(Q)$(CC) -c $(CFLAGS) -o $@ $<
 
 VMLINUX_BTF_PATHS ?= $(if $(O),$(O)/vmlinux)				\
 		     $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux)	\
@@ -181,15 +185,15 @@ $(BPFOBJ): $(wildcard $(BPFDIR)/*.[ch] $(BPFDIR)/Makefile)		       \
 
 $(BUILD_DIR)/libbpf $(BUILD_DIR)/bpftool $(BUILD_DIR)/resolve_btfids $(INCLUDE_DIR):
 	$(call msg,MKDIR,,$@)
-	mkdir -p $@
+	$(Q)mkdir -p $@
 
 $(INCLUDE_DIR)/vmlinux.h: $(VMLINUX_BTF) | $(BPFTOOL) $(INCLUDE_DIR)
 ifeq ($(VMLINUX_H),)
 	$(call msg,GEN,,$@)
-	$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@
+	$(Q)$(BPFTOOL) btf dump file $(VMLINUX_BTF) format c > $@
 else
 	$(call msg,CP,,$@)
-	cp "$(VMLINUX_H)" $@
+	$(Q)cp "$(VMLINUX_H)" $@
 endif
 
 $(RESOLVE_BTFIDS): $(BPFOBJ) | $(BUILD_DIR)/resolve_btfids	\
@@ -238,28 +242,28 @@ $(OUTPUT)/flow_dissector_load.o: flow_dissector_load.h
 # $4 - LDFLAGS
 define CLANG_BPF_BUILD_RULE
 	$(call msg,CLNG-LLC,$(TRUNNER_BINARY),$2)
-	($(CLANG) $3 -O2 -target bpf -emit-llvm				\
+	$(Q)($(CLANG) $3 -O2 -target bpf -emit-llvm			\
 		-c $1 -o - || echo "BPF obj compilation failed") | 	\
 	$(LLC) -mattr=dwarfris -march=bpf -mcpu=v3 $4 -filetype=obj -o $2
 endef
 # Similar to CLANG_BPF_BUILD_RULE, but with disabled alu32
 define CLANG_NOALU32_BPF_BUILD_RULE
 	$(call msg,CLNG-LLC,$(TRUNNER_BINARY),$2)
-	($(CLANG) $3 -O2 -target bpf -emit-llvm				\
+	$(Q)($(CLANG) $3 -O2 -target bpf -emit-llvm			\
 		-c $1 -o - || echo "BPF obj compilation failed") | 	\
 	$(LLC) -march=bpf -mcpu=v2 $4 -filetype=obj -o $2
 endef
 # Similar to CLANG_BPF_BUILD_RULE, but using native Clang and bpf LLC
 define CLANG_NATIVE_BPF_BUILD_RULE
 	$(call msg,CLNG-BPF,$(TRUNNER_BINARY),$2)
-	($(CLANG) $3 -O2 -emit-llvm					\
+	$(Q)($(CLANG) $3 -O2 -emit-llvm					\
 		-c $1 -o - || echo "BPF obj compilation failed") | 	\
 	$(LLC) -march=bpf -mcpu=v3 $4 -filetype=obj -o $2
 endef
 # Build BPF object using GCC
 define GCC_BPF_BUILD_RULE
 	$(call msg,GCC-BPF,$(TRUNNER_BINARY),$2)
-	$(BPF_GCC) $3 $4 -O2 -c $1 -o $2
+	$(Q)$(BPF_GCC) $3 $4 -O2 -c $1 -o $2
 endef
 
 SKEL_BLACKLIST := btf__% test_pinning_invalid.c test_sk_assign.c
@@ -301,7 +305,7 @@ ifeq ($($(TRUNNER_OUTPUT)-dir),)
 $(TRUNNER_OUTPUT)-dir := y
 $(TRUNNER_OUTPUT):
 	$$(call msg,MKDIR,,$$@)
-	mkdir -p $$@
+	$(Q)mkdir -p $$@
 endif
 
 # ensure we set up BPF objects generation rule just once for a given
@@ -321,7 +325,7 @@ $(TRUNNER_BPF_SKELS): $(TRUNNER_OUTPUT)/%.skel.h:			\
 		      $(TRUNNER_OUTPUT)/%.o				\
 		      | $(BPFTOOL) $(TRUNNER_OUTPUT)
 	$$(call msg,GEN-SKEL,$(TRUNNER_BINARY),$$@)
-	$$(BPFTOOL) gen skeleton $$< > $$@
+	$(Q)$$(BPFTOOL) gen skeleton $$< > $$@
 endif
 
 # ensure we set up tests.h header generation rule just once
@@ -345,30 +349,30 @@ $(TRUNNER_TEST_OBJS): $(TRUNNER_OUTPUT)/%.test.o:			\
 		      $(TRUNNER_BPF_SKELS)				\
 		      $$(BPFOBJ) | $(TRUNNER_OUTPUT)
 	$$(call msg,TEST-OBJ,$(TRUNNER_BINARY),$$@)
-	cd $$(@D) && $$(CC) -I. $$(CFLAGS) -c $(CURDIR)/$$< $$(LDLIBS) -o $$(@F)
+	$(Q)cd $$(@D) && $$(CC) -I. $$(CFLAGS) -c $(CURDIR)/$$< $$(LDLIBS) -o $$(@F)
 
 $(TRUNNER_EXTRA_OBJS): $(TRUNNER_OUTPUT)/%.o:				\
 		       %.c						\
 		       $(TRUNNER_EXTRA_HDRS)				\
 		       $(TRUNNER_TESTS_HDR)				\
 		       $$(BPFOBJ) | $(TRUNNER_OUTPUT)
 	$$(call msg,EXT-OBJ,$(TRUNNER_BINARY),$$@)
-	$$(CC) $$(CFLAGS) -c $$< $$(LDLIBS) -o $$@
+	$(Q)$$(CC) $$(CFLAGS) -c $$< $$(LDLIBS) -o $$@
 
 # only copy extra resources if in flavored build
 $(TRUNNER_BINARY)-extras: $(TRUNNER_EXTRA_FILES) | $(TRUNNER_OUTPUT)
 ifneq ($2,)
 	$$(call msg,EXT-COPY,$(TRUNNER_BINARY),$(TRUNNER_EXTRA_FILES))
-	cp -a $$^ $(TRUNNER_OUTPUT)/
+	$(Q)cp -a $$^ $(TRUNNER_OUTPUT)/
 endif
 
 $(OUTPUT)/$(TRUNNER_BINARY): $(TRUNNER_TEST_OBJS)			\
 			     $(TRUNNER_EXTRA_OBJS) $$(BPFOBJ)		\
 			     $(RESOLVE_BTFIDS)				\
 			     | $(TRUNNER_BINARY)-extras
 	$$(call msg,BINARY,,$$@)
-	$$(CC) $$(CFLAGS) $$(filter %.a %.o,$$^) $$(LDLIBS) -o $$@
-	$(RESOLVE_BTFIDS) --no-fail --btf btf_data.o $$@
+	$(Q)$$(CC) $$(CFLAGS) $$(filter %.a %.o,$$^) $$(LDLIBS) -o $$@
+	$(Q)$(RESOLVE_BTFIDS) --no-fail --btf btf_data.o $$@
 
 endef
 
@@ -421,17 +425,17 @@ verifier/tests.h: verifier/*.c
 		) > verifier/tests.h)
 $(OUTPUT)/test_verifier: test_verifier.c verifier/tests.h $(BPFOBJ) | $(OUTPUT)
 	$(call msg,BINARY,,$@)
-	$(CC) $(CFLAGS) $(filter %.a %.o %.c,$^) $(LDLIBS) -o $@
+	$(Q)$(CC) $(CFLAGS) $(filter %.a %.o %.c,$^) $(LDLIBS) -o $@
 
 # Make sure we are able to include and link libbpf against c++.
 $(OUTPUT)/test_cpp: test_cpp.cpp $(OUTPUT)/test_core_extern.skel.h $(BPFOBJ)
 	$(call msg,CXX,,$@)
-	$(CXX) $(CFLAGS) $^ $(LDLIBS) -o $@
+	$(Q)$(CXX) $(CFLAGS) $^ $(LDLIBS) -o $@
 
 # Benchmark runner
 $(OUTPUT)/bench_%.o: benchs/bench_%.c bench.h
 	$(call msg,CC,,$@)
-	$(CC) $(CFLAGS) -c $(filter %.c,$^) $(LDLIBS) -o $@
+	$(Q)$(CC) $(CFLAGS) -c $(filter %.c,$^) $(LDLIBS) -o $@
 $(OUTPUT)/bench_rename.o: $(OUTPUT)/test_overhead.skel.h
 $(OUTPUT)/bench_trigger.o: $(OUTPUT)/trigger_bench.skel.h
 $(OUTPUT)/bench_ringbufs.o: $(OUTPUT)/ringbuf_bench.skel.h \
@@ -444,7 +448,7 @@ $(OUTPUT)/bench: $(OUTPUT)/bench.o $(OUTPUT)/testing_helpers.o \
 		 $(OUTPUT)/bench_trigger.o \
 		 $(OUTPUT)/bench_ringbufs.o
 	$(call msg,BINARY,,$@)
-	$(CC) $(LDFLAGS) -o $@ $(filter %.a %.o,$^) $(LDLIBS)
+	$(Q)$(CC) $(LDFLAGS) -o $@ $(filter %.a %.o,$^) $(LDLIBS)
 
 EXTRA_CLEAN := $(TEST_CUSTOM_PROGS) $(SCRATCH_DIR)			\
 	prog_tests/tests.h map_tests/tests.h verifier/tests.h		\