From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Quentin Monnet <quentin.monnet@netronome.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>, lkml <linux-kernel@vger.kernel.org>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
Ingo Molnar <mingo@kernel.org>,
Namhyung Kim <namhyung@kernel.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Michael Petlan <mpetlan@redhat.com>,
Jesper Dangaard Brouer <brouer@redhat.com>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>
Subject: Re: [PATCH bpf v2] bpftool: Allow to link libbpf dynamically
Date: Thu, 28 Nov 2019 16:52:20 +0100 [thread overview]
Message-ID: <871rtsvw0b.fsf@toke.dk> (raw)
In-Reply-To: <497b4151-9aad-f3a9-3aff-78d665e5f750@netronome.com>
Quentin Monnet <quentin.monnet@netronome.com> writes:
> 2019-11-28 15:53 UTC+0100 ~ Toke Høiland-Jørgensen <toke@redhat.com>
>> From: Jiri Olsa <jolsa@kernel.org>
>>
>> Currently we support only static linking with kernel's libbpf
>> (tools/lib/bpf). This patch adds LIBBPF_DYNAMIC compile variable
>> that triggers libbpf detection and bpf dynamic linking:
>>
>> $ make -C tools/bpf/bpftool make LIBBPF_DYNAMIC=1
>>
>> If libbpf is not installed, build (with LIBBPF_DYNAMIC=1) stops with:
>>
>> $ make -C tools/bpf/bpftool LIBBPF_DYNAMIC=1
>> Auto-detecting system features:
>> ... libbfd: [ on ]
>> ... disassembler-four-args: [ on ]
>> ... zlib: [ on ]
>> ... libbpf: [ OFF ]
>>
>> Makefile:102: *** Error: No libbpf devel library found, please install-devel or libbpf-dev.
>>
>> Adding LIBBPF_DIR compile variable to allow linking with
>> libbpf installed into specific directory:
>>
>> $ make -C tools/lib/bpf/ prefix=/tmp/libbpf/ install_lib install_headers
>> $ make -C tools/bpf/bpftool/ LIBBPF_DYNAMIC=1 LIBBPF_DIR=/tmp/libbpf/
>>
>> It might be needed to clean build tree first because features
>> framework does not detect the change properly:
>>
>> $ make -C tools/build/feature clean
>> $ make -C tools/bpf/bpftool/ clean
>>
>> Since bpftool uses bits of libbpf that are not exported as public API in
>> the .so version, we also pass in libbpf.a to the linker, which allows it to
>> pick up the private functions from the static library without having to
>> expose them as ABI.
>>
>> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
>> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
>> ---
>> v2:
>> - Pass .a file to linker when dynamically linking, so bpftool can use
>> private functions from libbpf without exposing them as API.
>>
>> tools/bpf/bpftool/Makefile | 38 +++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 37 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
>> index 39bc6f0f4f0b..397051ed9e41 100644
>> --- a/tools/bpf/bpftool/Makefile
>> +++ b/tools/bpf/bpftool/Makefile
>> @@ -1,6 +1,15 @@
>> # SPDX-License-Identifier: GPL-2.0-only
>> +# LIBBPF_DYNAMIC to enable libbpf dynamic linking.
>> +
>> include ../../scripts/Makefile.include
>> include ../../scripts/utilities.mak
>> +include ../../scripts/Makefile.arch
>> +
>> +ifeq ($(LP64), 1)
>> + libdir_relative = lib64
>> +else
>> + libdir_relative = lib
>> +endif
>>
>> ifeq ($(srctree),)
>> srctree := $(patsubst %/,%,$(dir $(CURDIR)))
>> @@ -55,7 +64,7 @@ ifneq ($(EXTRA_LDFLAGS),)
>> LDFLAGS += $(EXTRA_LDFLAGS)
>> endif
>>
>> -LIBS = $(LIBBPF) -lelf -lz
>> +LIBS = -lelf -lz
>
> Hi Toke,
>
> You don't need to remove $(LIBBPF) here, because you add it in both
> cases below (whether $(LIBBPF_DYNAMIC) is defined or not).
Oh, right, good point; will fix :)
next prev parent reply other threads:[~2019-11-28 15:52 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-27 9:48 [PATCH 0/3] perf/bpftool: Allow to link libbpf dynamically Jiri Olsa
2019-11-27 9:48 ` [PATCH 1/3] perf tools: Allow to specify libbpf install directory Jiri Olsa
2019-11-27 9:48 ` [PATCH 2/3] libbpf: Export netlink functions used by bpftool Jiri Olsa
2019-11-27 9:48 ` [PATCH 3/3] bpftool: Allow to link libbpf dynamically Jiri Olsa
2019-11-27 13:38 ` Quentin Monnet
2019-11-27 14:15 ` Jiri Olsa
2019-11-27 14:24 ` Arnaldo Carvalho de Melo
2019-11-27 14:31 ` Quentin Monnet
2019-11-27 15:48 ` Arnaldo Carvalho de Melo
2019-11-27 15:52 ` Quentin Monnet
2019-11-27 15:59 ` Arnaldo Carvalho de Melo
2019-11-27 14:29 ` Quentin Monnet
2019-11-27 16:41 ` Alexei Starovoitov
2019-11-27 16:37 ` [PATCH 0/3] perf/bpftool: " Alexei Starovoitov
2019-11-27 18:44 ` Arnaldo Carvalho de Melo
2019-11-27 20:24 ` Andrii Nakryiko
2019-11-27 21:22 ` Daniel Borkmann
2019-11-27 22:47 ` Jiri Olsa
2019-11-28 9:06 ` Toke Høiland-Jørgensen
2019-11-28 14:53 ` [PATCH bpf v2] bpftool: " Toke Høiland-Jørgensen
2019-11-28 15:32 ` Quentin Monnet
2019-11-28 15:52 ` Toke Høiland-Jørgensen [this message]
2019-11-28 16:07 ` [PATCH bpf v3] " Toke Høiland-Jørgensen
2019-11-28 17:30 ` Quentin Monnet
2019-11-29 8:12 ` Jiri Olsa
2019-11-29 8:24 ` Toke Høiland-Jørgensen
2019-11-29 10:24 ` Daniel Borkmann
2019-11-29 14:00 ` Toke Høiland-Jørgensen
2019-11-29 23:56 ` Daniel Borkmann
2019-12-02 8:59 ` Jiri Olsa
2019-12-02 17:09 ` [PATCH 0/3] perf/bpftool: " Andrii Nakryiko
2019-12-02 18:08 ` Toke Høiland-Jørgensen
2019-12-02 18:42 ` Andrii Nakryiko
2019-12-02 18:54 ` Arnaldo Carvalho de Melo
2019-12-02 19:21 ` Jiri Olsa
2019-12-02 19:54 ` Andrii Nakryiko
2019-12-02 20:02 ` Jiri Olsa
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