On Thu, 30 Jun 2022 at 20:25, Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> wrote: > > 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? I'm not sure either, it looks like it's mostly a way to print that the lib is missing (when it's the case) before attempting to compile [0]. Probably something we can look into removing, I agree the feature test doesn't bring much here. We'll soon need a new test for the latest libbfd changes though [1]. [0] https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=d66fa3c70e598746a907e5db5ed024035e01817a [1] https://lore.kernel.org/bpf/20220622181918.ykrs5rsnmx3og4sv@xxxxxxxxxxxxxxxxx/
