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Date: Mon, 2 Dec 2019 09:59:30 +0100 From: Jiri Olsa <jolsa@...hat.com> To: Daniel Borkmann <daniel@...earbox.net> Cc: Toke Høiland-Jørgensen <toke@...hat.com>, Alexei Starovoitov <alexei.starovoitov@...il.com>, Jiri Olsa <jolsa@...nel.org>, lkml <linux-kernel@...r.kernel.org>, netdev@...r.kernel.org, bpf@...r.kernel.org, Ingo Molnar <mingo@...nel.org>, Namhyung Kim <namhyung@...nel.org>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Michael Petlan <mpetlan@...hat.com>, Jesper Dangaard Brouer <brouer@...hat.com>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, Andrii Nakryiko <andriin@...com>, Arnaldo Carvalho de Melo <acme@...nel.org>, kubakici@...pl Subject: Re: [PATCH bpf v3] bpftool: Allow to link libbpf dynamically On Sat, Nov 30, 2019 at 12:56:49AM +0100, Daniel Borkmann wrote: > On 11/29/19 3:00 PM, Toke Høiland-Jørgensen wrote: > > Daniel Borkmann <daniel@...earbox.net> writes: > > > On 11/28/19 5:07 PM, Toke Høiland-Jørgensen wrote: > > > > From: Jiri Olsa <jolsa@...nel.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. ok, will have separate patch for this > > 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. ok > > 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. ok, will send new version soon thanks, jirka > > Thanks, > Daniel >
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