| Message ID | 20210203203445.3356114-1-andrii@kernel.org (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 5f10c1aac8b29d225d19a74656865d1ee3db6eaa |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf-next] libbpf: stop using feature-detection Makefiles | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for bpf-next |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | warning | 6 maintainers not CCed: songliubraving@fb.com john.fastabend@gmail.com kpsingh@kernel.org ast@kernel.org kafai@fb.com yhs@fb.com |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 87 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
| netdev/stable | success | Stable not CCed |
Andrii Nakryiko wrote: > 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). > > Cc: Arnaldo Carvalho de Melo <acme@redhat.com> > Cc: Randy Dunlap <rdunlap@infradead.org> > Signed-off-by: Andrii Nakryiko <andrii@kernel.org> > --- > tools/lib/bpf/.gitignore | 1 - > tools/lib/bpf/Makefile | 47 ++++------------------------------------ > 2 files changed, 4 insertions(+), 44 deletions(-) I've also hit these annoying cases at least once or twice. Acked-by: John Fastabend <john.fastabend@gmail.com>
On 2/3/21 12:34 PM, Andrii Nakryiko wrote: > 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). > > Cc: Arnaldo Carvalho de Melo <acme@redhat.com> > Cc: Randy Dunlap <rdunlap@infradead.org> > Signed-off-by: Andrii Nakryiko <andrii@kernel.org> > --- > tools/lib/bpf/.gitignore | 1 - > tools/lib/bpf/Makefile | 47 ++++------------------------------------ > 2 files changed, 4 insertions(+), 44 deletions(-) Hi Andrii, This does indeed fix the build problems that I was seeing, so I can add: Acked-by: Randy Dunlap <rdunlap@infradead.org> but in the long term I think that features/libs/etc. that are used should be checked for instead of being used blindly... IMO. Thanks.
Hello: This patch was applied to bpf/bpf-next.git (refs/heads/master): On Wed, 3 Feb 2021 12:34:45 -0800 you wrote: > 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. > > [...] Here is the summary with links: - [bpf-next] libbpf: stop using feature-detection Makefiles https://git.kernel.org/bpf/bpf-next/c/5f10c1aac8b2 You are awesome, thank you! -- Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html
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 55bd78b3496f..887a494ad5fc 100644 --- a/tools/lib/bpf/Makefile +++ b/tools/lib/bpf/Makefile @@ -58,28 +58,7 @@ 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
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). Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> --- tools/lib/bpf/.gitignore | 1 - tools/lib/bpf/Makefile | 47 ++++------------------------------------ 2 files changed, 4 insertions(+), 44 deletions(-)