Commit b79c2ce3 authored by Quentin Monnet's avatar Quentin Monnet Committed by Andrii Nakryiko
Browse files

libbpf: Skip re-installing headers file if source is older than target 



The "install_headers" target in libbpf's Makefile would unconditionally
export all API headers to the target directory. When those headers are
installed to compile another application, this means that make always
finds newer dependencies for the source files relying on those headers,
and deduces that the targets should be rebuilt.

Avoid that by making "install_headers" depend on the source header
files, and (re-)install them only when necessary.

Signed-off-by: default avatarQuentin Monnet <quentin@isovalent.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211007194438.34443-2-quentin@isovalent.com
parent 7e3cbd34

tools/lib/bpf/Makefile

+18 −9
Original line number Diff line number Diff line
@@ -241,15 +241,24 @@ install_lib: all_cmd 
		$(call do_install_mkdir,$(libdir_SQ)); \

		cp -fpR $(LIB_FILE) $(DESTDIR)$(libdir_SQ)



INSTALL_HEADERS = bpf.h libbpf.h btf.h libbpf_common.h libbpf_legacy.h xsk.h \

		  bpf_helpers.h $(BPF_GENERATED) bpf_tracing.h		     \

		  bpf_endian.h bpf_core_read.h skel_internal.h		     \

		  libbpf_version.h



install_headers: $(BPF_GENERATED)

	$(call QUIET_INSTALL, headers)					     \

		$(foreach hdr,$(INSTALL_HEADERS),			     \

			$(call do_install,$(hdr),$(prefix)/include/bpf,644);)

SRC_HDRS := bpf.h libbpf.h btf.h libbpf_common.h libbpf_legacy.h xsk.h	     \

	    bpf_helpers.h bpf_tracing.h bpf_endian.h bpf_core_read.h	     \

	    skel_internal.h libbpf_version.h

GEN_HDRS := $(BPF_GENERATED)



INSTALL_PFX := $(DESTDIR)$(prefix)/include/bpf

INSTALL_SRC_HDRS := $(addprefix $(INSTALL_PFX)/, $(SRC_HDRS))

INSTALL_GEN_HDRS := $(addprefix $(INSTALL_PFX)/, $(notdir $(GEN_HDRS)))



$(INSTALL_SRC_HDRS): $(INSTALL_PFX)/%.h: %.h

	$(call QUIET_INSTALL, $@) \

		$(call do_install,$<,$(prefix)/include/bpf,644)



$(INSTALL_GEN_HDRS): $(INSTALL_PFX)/%.h: $(OUTPUT)%.h

	$(call QUIET_INSTALL, $@) \

		$(call do_install,$<,$(prefix)/include/bpf,644)



install_headers: $(BPF_GENERATED) $(INSTALL_SRC_HDRS) $(INSTALL_GEN_HDRS)



install_pkgconfig: $(PC_FILE)

	$(call QUIET_INSTALL, $(PC_FILE)) \