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From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	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 v3] bpftool: Allow to link libbpf dynamically
Date: Fri, 29 Nov 2019 09:24:53 +0100	[thread overview]
Message-ID: <87v9r3um22.fsf@toke.dk> (raw)
In-Reply-To: <20191129081251.GA14169@krava>

Jiri Olsa <jolsa@redhat.com> writes:

> On Thu, Nov 28, 2019 at 05:07:12PM +0100, Toke Høiland-Jørgensen wrote:
>
> SNIP
>
>>  ifeq ($(srctree),)
>>  srctree := $(patsubst %/,%,$(dir $(CURDIR)))
>> @@ -63,6 +72,19 @@ RM ?= rm -f
>>  FEATURE_USER = .bpftool
>>  FEATURE_TESTS = libbfd disassembler-four-args reallocarray zlib
>>  FEATURE_DISPLAY = libbfd disassembler-four-args zlib
>> +ifdef LIBBPF_DYNAMIC
>> +  FEATURE_TESTS   += libbpf
>> +  FEATURE_DISPLAY += libbpf
>> +
>> +  # for linking with debug library run:
>> +  # make LIBBPF_DYNAMIC=1 LIBBPF_DIR=/opt/libbpf
>> +  ifdef LIBBPF_DIR
>> +    LIBBPF_CFLAGS  := -I$(LIBBPF_DIR)/include
>> +    LIBBPF_LDFLAGS := -L$(LIBBPF_DIR)/$(libdir_relative)
>> +    FEATURE_CHECK_CFLAGS-libbpf  := $(LIBBPF_CFLAGS)
>> +    FEATURE_CHECK_LDFLAGS-libbpf := $(LIBBPF_LDFLAGS)
>> +  endif
>> +endif
>>  
>>  check_feat := 1
>>  NON_CHECK_FEAT_TARGETS := clean uninstall doc doc-clean doc-install doc-uninstall
>> @@ -88,6 +110,18 @@ ifeq ($(feature-reallocarray), 0)
>>  CFLAGS += -DCOMPAT_NEED_REALLOCARRAY
>>  endif
>>  
>> +ifdef LIBBPF_DYNAMIC
>> +  ifeq ($(feature-libbpf), 1)
>> +    # bpftool uses non-exported functions from libbpf, so just add the dynamic
>> +    # version of libbpf and let the linker figure it out
>> +    LIBS    := -lbpf $(LIBS)
>
> nice, so linker will pick up the missing symbols and we
> don't need to check on particular libbpf version then

Yup, exactly. I verified with objdump that the end result is a
dynamically linked bpftool with LIBBPF_DYNAMIC is set, and a statically
linked one if it isn't; so the linker seems to be smart enough to just
figure out how to do the right thing :)

-Toke


  reply	other threads:[~2019-11-29  8:25 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
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 [this message]
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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