Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 10 Jan 2023 11:46:14 -0300
From:   Arnaldo Carvalho de Melo <acme@kernel.org>
To:     Ian Rogers <irogers@google.com>
Cc:     Jiri Olsa <olsajiri@gmail.com>, Mike Leach <mike.leach@linaro.org>,
        linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
        bpf@vger.kernel.org, peterz@infradead.org, mingo@redhat.com,
        mark.rutland@arm.com, alexander.shishkin@linux.intel.com,
        namhyung@kernel.org
Subject: Re: [PATCH v3 1/2] perf build: Properly guard libbpf includes
Message-ID: <Y716Nt3c/Lc0Z4P5@kernel.org>
References: <CAJ9a7ViGE3UJX02oA42A9TSTKsOozPzdHjyL+OSP4J-9dZFqrg@mail.gmail.com>
 <Y7hZccgOiueB31a+@kernel.org>
 <Y7hgKMDGzQlankL1@kernel.org>
 <Y7hgoVKBoulCbA4l@kernel.org>
 <CAP-5=fXPPSHvN6VYc=8tzBz4xtKg4Ofa17zV4pAk0ycorXje8w@mail.gmail.com>
 <Y7wuz6EOggZ8Wysb@kernel.org>
 <Y7xYimp0h4YT72/N@krava>
 <CAP-5=fXwO5_kK=pMV09jdAVw386CB0JwArD0BZd=B=xCyWSP1g@mail.gmail.com>
 <CAP-5=fVa51_URGsdDFVTzpyGmdDRj_Dj2EKPuDHNQ0BYgMSzUA@mail.gmail.com>
 <Y712sCnYBJobe2eY@kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <Y712sCnYBJobe2eY@kernel.org>
Precedence: bulk

Em Tue, Jan 10, 2023 at 11:31:12AM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Mon, Jan 09, 2023 at 11:29:51AM -0800, Ian Rogers escreveu:
> > On Mon, Jan 9, 2023 at 10:37 AM Ian Rogers <irogers@google.com> wrote:
> > > -int libbpf_register_prog_handler(const char *sec __maybe_unused,
> > > -                                 enum bpf_prog_type prog_type __maybe_unused,
> > > -                                 enum bpf_attach_type exp_attach_type
> > > __maybe_unused,
> > > -                                 const struct
> > > libbpf_prog_handler_opts *opts __maybe_unused)
> > > +static int libbpf_register_prog_handler(const char *sec __maybe_unused,
> > > +                                       enum bpf_prog_type prog_type
> > > __maybe_unused,
> > > +                                       enum bpf_attach_type
> > > exp_attach_type __maybe_unused,
> > > +                                       const void *opts __maybe_unused)
> > > {
> > >        pr_err("%s: not support, update libbpf\n", __func__);
> > >        return -ENOTSUP;
> > > ```
> > >
> > > There are some other fixes necessary too. I'll try to write the fuller
> > > patch but I have no means for testing except for undefining
> > > HAVE_LIBBPF_BPF_PROGRAM__SET_INSNS.
> > 
> > So libbpf_prog_handler_opts is missing in the failing build, this
> > points to a libbpf before 0.8. I'm somewhat concerned that to work
> > around these linkage problems we're adding runtime errors - we may
> > build but the functionality is totally crippled. Is it worth
> > maintaining these broken builds or to just upfront fail the feature
> > test?
 
> Probably better to make the feature test disable bpf support while
> emitting a warning that features such as a, b, and c won't we available.

This would be the one-liner I think is appropriate for v6.2, ok?

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 9962ae23ab8c5868..5b87846759036f6f 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -589,6 +589,8 @@ ifndef NO_LIBELF
           $(call feature_check,libbpf-bpf_program__set_insns)
           ifeq ($(feature-libbpf-bpf_program__set_insns), 1)
             CFLAGS += -DHAVE_LIBBPF_BPF_PROGRAM__SET_INSNS
+          else
+            dummy := $(error Error: libbpf devel library needs to be >= 0.8.0 to build with LIBBPF_DYNAMIC, update or build statically with the version that comes with the kernel sources);
           endif
           $(call feature_check,libbpf-btf__raw_data)
           ifeq ($(feature-libbpf-btf__raw_data), 1)