Messages in this thread | | | Subject | Re: [PATCH bpf v3] bpftool: Allow to link libbpf dynamically | From | Daniel Borkmann <> | Date | Sat, 30 Nov 2019 00:56:49 +0100 |
| |
On 11/29/19 3:00 PM, Toke Høiland-Jørgensen wrote: > Daniel Borkmann <daniel@iogearbox.net> writes: >> On 11/28/19 5:07 PM, Toke Høiland-Jørgensen wrote: >>> From: Jiri Olsa <jolsa@kernel.org> [...] >>> ifeq ($(srctree),) >>> srctree := $(patsubst %/,%,$(dir $(CURDIR))) >>> @@ -63,6 +72,19 @@ RM ?= rm -f >>> FEATURE_USER = .bpftool >>> FEATURE_TESTS = libbfd disassembler-four-args reallocarray zlib >>> FEATURE_DISPLAY = libbfd disassembler-four-args zlib >>> +ifdef LIBBPF_DYNAMIC >>> + FEATURE_TESTS += libbpf >>> + FEATURE_DISPLAY += libbpf >>> + >>> + # for linking with debug library run: >>> + # make LIBBPF_DYNAMIC=1 LIBBPF_DIR=/opt/libbpf >> >> The Makefile already has BPF_DIR which points right now to >> '$(srctree)/tools/lib/bpf/' and LIBBPF_PATH for the final one and >> where $(LIBBPF_PATH)libbpf.a is expected to reside. Can't we improve >> the Makefile to reuse and work with these instead of adding yet >> another LIBBPF_DIR var which makes future changes in this area more >> confusing? The libbpf build spills out libbpf.{a,so*} by default >> anyway. > > I see what you mean; however, LIBBPF_DIR is meant to be specifically an > override for the dynamic library, not just the path to libbpf. > > Would it be less confusing to overload the LIBBPF_DYNAMIC variable > instead? I.e., > > make LIBBPF_DYNAMIC=1 > > would dynamically link against the libbpf installed in the system, but > > make LIBBPF_DYNAMIC=/opt/libbpf > > would override that and link against whatever is in /opt/libbpf instead? > WDYT?
Hm, given perf tool has similar LIB*_DIR vars in place for its libs, it probably makes sense to stick with this convention as well then. Perhaps better in this case to just rename s/BPF_DIR/BPF_SRC_DIR/, s/LIBBPF_OUTPUT/LIBBPF_BUILD_OUTPUT/, and s/LIBBPF_PATH/LIBBPF_BUILD_PATH/ to make their purpose more clear.
One thing that would be good to do as well for this patch is to:
i) Document both LIBBPF_DYNAMIC and LIBBPF_DIR in the Makefile comment you added at the top along with a simple usage example.
ii) Extend tools/testing/selftests/bpf/test_bpftool_build.sh with a dynamic linking test case, e.g. building libbpf into a temp dir and pointing LIBBPF_DIR to it for bpftool LIBBPF_DYNAMIC=1 build.
Thanks, Daniel
| |