On 30/06/2022 16:16, Daniel Borkmann wrote: > On 6/29/22 4:39 PM, Quentin Monnet wrote: >> Some dependencies for bpftool are optional, and the associated features >> may be left aside at compilation time depending on the available >> components on the system (libraries, BTF, clang version, etc.). >> Sometimes, it is useful to explicitly leave some of those features aside >> when compiling, even though the system would support them. For example, >> this can be useful: >> >> - for testing bpftool's behaviour when the feature is not present, >> - for copmiling for a different system, where some libraries are >> missing, >> - for producing a lighter binary, >> - for disabling features that do not compile correctly on older >> systems - although this is not supposed to happen, this is >> currently the case for skeletons support on Linux < 5.15, where >> struct bpf_perf_link is not defined in kernel BTF. >> >> For such cases, we introduce, in the Makefile, some environment >> variables that can be used to disable those features: namely, >> BPFTOOL_FEATURE_NO_LIBBFD, BPFTOOL_FEATURE_NO_LIBCAP, and >> BPFTOOL_FEATURE_NO_SKELETONS. >> >> Signed-off-by: Quentin Monnet <quentin@xxxxxxxxxxxxx> >> --- >> tools/bpf/bpftool/Makefile | 20 ++++++++++++++++++-- >> 1 file changed, 18 insertions(+), 2 deletions(-) >> >> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile >> index c19e0e4c41bd..b3dd6a1482f6 100644 >> --- a/tools/bpf/bpftool/Makefile >> +++ b/tools/bpf/bpftool/Makefile >> @@ -93,8 +93,24 @@ INSTALL ?= install >> RM ?= rm -f >> FEATURE_USER = .bpftool >> -FEATURE_TESTS = libbfd disassembler-four-args zlib libcap \ >> - clang-bpf-co-re >> +FEATURE_TESTS := disassembler-four-args zlib >> + >> +# Disable libbfd (for disassembling JIT-compiled programs) by setting >> +# BPFTOOL_FEATURE_NO_LIBBFD >> +ifeq ($(BPFTOOL_FEATURE_NO_LIBBFD),) >> + FEATURE_TESTS += libbfd >> +endif >> +# Disable libcap (for probing features available to unprivileged >> users) by >> +# setting BPFTOOL_FEATURE_NO_LIBCAP >> +ifeq ($(BPFTOOL_FEATURE_NO_LIBCAP),) >> + FEATURE_TESTS += libcap >> +endif > > The libcap one I think is not really crucial, so that lgtm. The other > ones I would > keep as requirement so we don't encourage distros to strip away needed > functionality > for odd reasons. At min, I think the libbfd is a must, imho. Thanks Daniel, that's a legitimate concern. Probably best to avoid offering an easy option to disable the features in that case - I can live with Makefile edits if I need to test a different feature set. Please drop this patch. Thanks, Quentin
