Pass all individual BPF object files (generated from progs/*.c) through `bpftool gen object` command to validate that BPF static linker doesn't corrupt them. As an additional sanity checks, validate that passing resulting object files through linker again results in identical ELF files. Exact same ELF contents can be guaranteed only after two passes, as after the first pass ELF sections order changes, and thus .BTF.ext data sections order changes. That, in turn, means that strings are added into the final BTF string sections in different order, so .BTF strings data might not be exactly the same. But doing another round of linking afterwards should result in the identical ELF file, which is checked with additional `diff` command. Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx> --- tools/testing/selftests/bpf/Makefile | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile index dbca39f45382..3a7c02add70c 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -355,12 +355,13 @@ $(TRUNNER_BPF_OBJS): $(TRUNNER_OUTPUT)/%.o: \ $$(call $(TRUNNER_BPF_BUILD_RULE),$$<,$$@, \ $(TRUNNER_BPF_CFLAGS)) -$(TRUNNER_BPF_SKELS): $(TRUNNER_OUTPUT)/%.skel.h: \ - $(TRUNNER_OUTPUT)/%.o \ - $(BPFTOOL) \ - | $(TRUNNER_OUTPUT) +$(TRUNNER_BPF_SKELS): %.skel.h: %.o $(BPFTOOL) | $(TRUNNER_OUTPUT) $$(call msg,GEN-SKEL,$(TRUNNER_BINARY),$$@) - $(Q)$$(BPFTOOL) gen skeleton $$< > $$@ + $(Q)$$(BPFTOOL) gen object $$(<:.o=.linked.o) $$< + $(Q)$$(BPFTOOL) gen object $$(<:.o=.linked2.o) $$(<:.o=.linked.o) + $(Q)$$(BPFTOOL) gen object $$(<:.o=.linked3.o) $$(<:.o=.linked2.o) + $(Q)diff $$(<:.o=.linked2.o) $$(<:.o=.linked3.o) + $(Q)$$(BPFTOOL) gen skeleton $$(<:.o=.linked.o) name $$(notdir $$(<:.o=)) > $$@ endif # ensure we set up tests.h header generation rule just once -- 2.30.2
