On Wed, Jun 29, 2022 at 7:40 AM Quentin Monnet <quentin@xxxxxxxxxxxxx> 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 as an aside, zlib is not really optional, libbpf depends on it and bpftool depends on libbpf, so... what's the point of a feature test? > + > +# 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 > +# Disable skeletons (e.g. for profiling programs or showing PIDs of processes > +# associated to BPF objects) by setting BPFTOOL_FEATURE_NO_SKELETONS > +ifeq ($(BPFTOOL_FEATURE_NO_SKELETONS),) > + FEATURE_TESTS += clang-bpf-co-re > +endif > + > FEATURE_DISPLAY = libbfd disassembler-four-args zlib libcap \ > clang-bpf-co-re > > -- > 2.34.1 >
