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From:   Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Date:   Tue, 26 Nov 2019 10:38:06 -0300
To:     Jiri Olsa <jolsa@kernel.org>
Cc:     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>,
        Toke =?iso-8859-1?Q?H=F8iland-J=F8rgensen?= <toke@redhat.com>,
        Jesper Dangaard Brouer <brouer@redhat.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        Andrii Nakryiko <andriin@fb.com>
Subject: Re: [PATCH] perf tools: Allow to link with libbpf dynamicaly
Message-ID: <20191126133806.GA19483@kernel.org>
References: <20191126121253.28253-1-jolsa@kernel.org>
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Em Tue, Nov 26, 2019 at 01:12:53PM +0100, Jiri Olsa escreveu:
> Currently we support only static linking with kernel's
> libbpf (tools/lib/bpf). This patch adds libbpf package
> detection and support to link perf with it dynamically.
> 
> The libbpf package status is displayed with:
> 
>   $ make VF=1
>   Auto-detecting system features:
>   ...
>   ...                        libbpf: [ on  ]
> 
> It's not checked by default, because it's quite new.
> Once it's on most distros we can switch it on.
> 
> For the same reason it's not added to the test-all check.
> 
> Perf does not need advanced version of libbpf, so we can
> check just for the base bpf_object__open function.
> 
> Adding new compile variable to detect libbpf package and
> link bpf dynamically:
> 
>   $ make LIBBPF_DYNAMIC=1
>     ...
>     LINK     perf
>   $ ldd perf | grep bpf
>     libbpf.so.0 => /lib64/libbpf.so.0 (0x00007f46818bc000)
> 
> If libbpf is not installed, build stops with:
> 
>   Makefile.config:486: *** Error: No libbpf devel library found,\
>   please install libbpf-devel.  Stop.

Thanks, tested with how I build it:

      $ make LIBBPF_DYNAMIC=1 -C tools/perf O=/tmp/build/perf
      make: Entering directory '/home/acme/git/perf/tools/perf'
        BUILD:   Doing 'make -j8' parallel build
      Makefile.config:493: *** Error: No libbpf devel library found, please install libbpf-devel.  Stop.
      make[1]: *** [Makefile.perf:225: sub-make] Error 2
      make: *** [Makefile:70: all] Error 2
      make: Leaving directory '/home/acme/git/perf/tools/perf'
      $

works as well as advertised, applied.

- Arnaldo