From: Andrii Nakryiko andrii@kernel.org
mainline inclusion from mainline-5.12-rc1 commit 5f10c1aac8b29d225d19a74656865d1ee3db6eaa category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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Libbpf's Makefile relies on Linux tools infrastructure's feature detection framework, but libbpf's needs are very modest: it detects the presence of libelf and libz, both of which are mandatory. So it doesn't benefit much from the framework, but pays significant costs in terms of maintainability and debugging experience, when something goes wrong. The other feature detector, testing for the presernce of minimal BPF API in system headers is long obsolete as well, providing no value.
So stop using feature detection and just assume the presence of libelf and libz during build time. Worst case, user will get a clear and actionable linker error, e.g.:
/usr/bin/ld: cannot find -lelf
On the other hand, we completely bypass recurring issues various users reported over time with false negatives of feature detection (libelf or libz not being detected, while they are actually present in the system).
Signed-off-by: Andrii Nakryiko andrii@kernel.org Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: John Fastabend john.fastabend@gmail.com Acked-by: Randy Dunlap rdunlap@infradead.org Link: https://lore.kernel.org/bpf/20210203203445.3356114-1-andrii@kernel.org (cherry picked from commit 5f10c1aac8b29d225d19a74656865d1ee3db6eaa) Signed-off-by: Wang Yufen wangyufen@huawei.com --- tools/lib/bpf/.gitignore | 1 - tools/lib/bpf/Makefile | 47 ++++------------------------------------ 2 files changed, 4 insertions(+), 44 deletions(-)
diff --git a/tools/lib/bpf/.gitignore b/tools/lib/bpf/.gitignore index 8a81b3679d2b..5d4cfac671d5 100644 --- a/tools/lib/bpf/.gitignore +++ b/tools/lib/bpf/.gitignore @@ -1,7 +1,6 @@ # SPDX-License-Identifier: GPL-2.0-only libbpf_version.h libbpf.pc -FEATURE-DUMP.libbpf libbpf.so.* TAGS tags diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile index f2a353bba25f..76cf5ab8d00c 100644 --- a/tools/lib/bpf/Makefile +++ b/tools/lib/bpf/Makefile @@ -59,28 +59,7 @@ ifndef VERBOSE VERBOSE = 0 endif
-FEATURE_USER = .libbpf -FEATURE_TESTS = libelf zlib bpf -FEATURE_DISPLAY = libelf zlib bpf - INCLUDES = -I. -I$(srctree)/tools/include -I$(srctree)/tools/include/uapi -FEATURE_CHECK_CFLAGS-bpf = $(INCLUDES) - -check_feat := 1 -NON_CHECK_FEAT_TARGETS := clean TAGS tags cscope help -ifdef MAKECMDGOALS -ifeq ($(filter-out $(NON_CHECK_FEAT_TARGETS),$(MAKECMDGOALS)),) - check_feat := 0 -endif -endif - -ifeq ($(check_feat),1) -ifeq ($(FEATURES_DUMP),) -include $(srctree)/tools/build/Makefile.feature -else -include $(FEATURES_DUMP) -endif -endif
export prefix libdir src obj
@@ -157,7 +136,7 @@ all: fixdep
all_cmd: $(CMD_TARGETS) check
-$(BPF_IN_SHARED): force elfdep zdep bpfdep $(BPF_HELPER_DEFS) +$(BPF_IN_SHARED): force $(BPF_HELPER_DEFS) @(test -f ../../include/uapi/linux/bpf.h -a -f ../../../include/uapi/linux/bpf.h && ( \ (diff -B ../../include/uapi/linux/bpf.h ../../../include/uapi/linux/bpf.h >/dev/null) || \ echo "Warning: Kernel ABI header at 'tools/include/uapi/linux/bpf.h' differs from latest version at 'include/uapi/linux/bpf.h'" >&2 )) || true @@ -175,7 +154,7 @@ $(BPF_IN_SHARED): force elfdep zdep bpfdep $(BPF_HELPER_DEFS) echo "Warning: Kernel ABI header at 'tools/include/uapi/linux/if_xdp.h' differs from latest version at 'include/uapi/linux/if_xdp.h'" >&2 )) || true $(Q)$(MAKE) $(build)=libbpf OUTPUT=$(SHARED_OBJDIR) CFLAGS="$(CFLAGS) $(SHLIB_FLAGS)"
-$(BPF_IN_STATIC): force elfdep zdep bpfdep $(BPF_HELPER_DEFS) +$(BPF_IN_STATIC): force $(BPF_HELPER_DEFS) $(Q)$(MAKE) $(build)=libbpf OUTPUT=$(STATIC_OBJDIR)
$(BPF_HELPER_DEFS): $(srctree)/tools/include/uapi/linux/bpf.h @@ -264,34 +243,16 @@ install_pkgconfig: $(PC_FILE)
install: install_lib install_pkgconfig install_headers
-### Cleaning rules - -config-clean: - $(call QUIET_CLEAN, feature-detect) - $(Q)$(MAKE) -C $(srctree)/tools/build/feature/ clean >/dev/null - -clean: config-clean +clean: $(call QUIET_CLEAN, libbpf) $(RM) -rf $(CMD_TARGETS) \ *~ .*.d .*.cmd LIBBPF-CFLAGS $(BPF_HELPER_DEFS) \ $(SHARED_OBJDIR) $(STATIC_OBJDIR) \ $(addprefix $(OUTPUT), \ *.o *.a *.so *.so.$(LIBBPF_MAJOR_VERSION) *.pc) - $(call QUIET_CLEAN, core-gen) $(RM) $(OUTPUT)FEATURE-DUMP.libbpf - -
-PHONY += force elfdep zdep bpfdep cscope tags +PHONY += force cscope tags force:
-elfdep: - @if [ "$(feature-libelf)" != "1" ]; then echo "No libelf found"; exit 1 ; fi - -zdep: - @if [ "$(feature-zlib)" != "1" ]; then echo "No zlib found"; exit 1 ; fi - -bpfdep: - @if [ "$(feature-bpf)" != "1" ]; then echo "BPF API too old"; exit 1 ; fi - cscope: ls *.c *.h > cscope.files cscope -b -q -I $(srctree)/include -f cscope.out