selftests/bpf: add bpf_call test

strip always_inline from test_l4lb.c and compile it with -fno-inline
to let verifier go through 11 function with various function arguments
and return values

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/testing/selftests/bpf/Makefile

@@ -17,7 +17,8 @@ TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test
 
 TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test_obj_id.o \
 	test_pkt_md_access.o test_xdp_redirect.o test_xdp_meta.o sockmap_parse_prog.o     \
-	sockmap_verdict_prog.o dev_cgroup.o sample_ret0.o test_tracepoint.o
+	sockmap_verdict_prog.o dev_cgroup.o sample_ret0.o test_tracepoint.o \
+	test_l4lb_noinline.o
 
 TEST_PROGS := test_kmod.sh test_xdp_redirect.sh test_xdp_meta.sh \
 	test_offload.py
@@ -49,8 +50,12 @@ else
   CPU ?= generic
 endif
 
+CLANG_FLAGS = -I. -I./include/uapi -I../../../include/uapi \
+	      -Wno-compare-distinct-pointer-types
+
+$(OUTPUT)/test_l4lb_noinline.o: CLANG_FLAGS += -fno-inline
+
 %.o: %.c
-	$(CLANG) -I. -I./include/uapi -I../../../include/uapi \
-		 -Wno-compare-distinct-pointer-types          \
+	$(CLANG) $(CLANG_FLAGS) \
 		 -O2 -target bpf -emit-llvm -c $< -o - |      \
 	$(LLC) -march=bpf -mcpu=$(CPU) -filetype=obj -o $@