netdev - Re: [PATCH 4/8] libbpf hashmap: Localize static hashmap_

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Date:   Fri, 15 May 2020 11:17:07 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Kajol Jain <kjain@...ux.ibm.com>,
        Andi Kleen <ak@...ux.intel.com>,
        John Garry <john.garry@...wei.com>,
        Jin Yao <yao.jin@...ux.intel.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Kim Phillips <kim.phillips@....com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Leo Yan <leo.yan@...aro.org>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 4/8] libbpf hashmap: Localize static hashmap__* symbols

On Thu, May 14, 2020 at 11:56:20PM -0700, Ian Rogers wrote:
> Localize the hashmap__* symbols in libbpf.a. To allow for a version in
> libapi.
> 
> Before:
> $ nm libbpf.a
> ...
> 000000000002088a t hashmap_add_entry
> 000000000001712a t hashmap__append
> 0000000000020aa3 T hashmap__capacity
> 000000000002099c T hashmap__clear
> 00000000000208b3 t hashmap_del_entry
> 0000000000020fc1 T hashmap__delete
> 0000000000020f29 T hashmap__find
> 0000000000020c6c t hashmap_find_entry
> 0000000000020a61 T hashmap__free
> 0000000000020b08 t hashmap_grow
> 00000000000208dd T hashmap__init
> 0000000000020d35 T hashmap__insert
> 0000000000020ab5 t hashmap_needs_to_grow
> 0000000000020947 T hashmap__new
> 0000000000000775 t hashmap__set
> 00000000000212f8 t hashmap__set
> 0000000000020a91 T hashmap__size
> ...
> 
> After:
> $ nm libbpf.a
> ...
> 000000000002088a t hashmap_add_entry
> 000000000001712a t hashmap__append
> 0000000000020aa3 t hashmap__capacity
> 000000000002099c t hashmap__clear
> 00000000000208b3 t hashmap_del_entry
> 0000000000020fc1 t hashmap__delete
> 0000000000020f29 t hashmap__find
> 0000000000020c6c t hashmap_find_entry
> 0000000000020a61 t hashmap__free
> 0000000000020b08 t hashmap_grow
> 00000000000208dd t hashmap__init
> 0000000000020d35 t hashmap__insert
> 0000000000020ab5 t hashmap_needs_to_grow
> 0000000000020947 t hashmap__new
> 0000000000000775 t hashmap__set
> 00000000000212f8 t hashmap__set
> 0000000000020a91 t hashmap__size
> ...

I think this will break bpf selftests which use hashmap,
we need to find some other way to include this

either to use it from libbpf directly, or use the api version
only if the libbpf is not compiled in perf, we could use
following to detect that:

      CFLAGS += -DHAVE_LIBBPF_SUPPORT
      $(call detected,CONFIG_LIBBPF)

jirka