linux-kernel - Re: [PATCH v2] perf tools: avoid sample_reg

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Date:   Mon, 30 Sep 2019 14:42:09 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc:     Ian Rogers <irogers@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>, linux-kernel@...r.kernel.org,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v2] perf tools: avoid sample_reg_masks being const + weak

On Mon, Sep 30, 2019 at 09:23:35AM -0300, Arnaldo Carvalho de Melo wrote:

SNIP

>   CC       /tmp/build/perf/util/lzma.o
>   CC       /tmp/build/perf/util/demangle-java.o
>   CC       /tmp/build/perf/util/demangle-rust.o
>   CC       /tmp/build/perf/util/jitdump.o
>   CC       /tmp/build/perf/util/genelf.o
>   CC       /tmp/build/perf/util/genelf_debug.o
>   CC       /tmp/build/perf/util/perf-hooks.o
>   CC       /tmp/build/perf/util/bpf-event.o
>   FLEX     /tmp/build/perf/util/parse-events-flex.c
>   LD       /tmp/build/perf/util/intel-pt-decoder/perf-in.o
>   FLEX     /tmp/build/perf/util/pmu-flex.c
>   CC       /tmp/build/perf/util/pmu-bison.o
>   CC       /tmp/build/perf/util/expr-bison.o
>   CC       /tmp/build/perf/util/parse-events.o
>   CC       /tmp/build/perf/util/parse-events-flex.o
>   CC       /tmp/build/perf/util/pmu.o
>   CC       /tmp/build/perf/util/pmu-flex.o
>   LD       /tmp/build/perf/util/perf-in.o
>   LD       /tmp/build/perf/perf-in.o
>   LINK     /tmp/build/perf/perf
> /usr/lib/gcc-cross/aarch64-linux-gnu/8/../../../../aarch64-linux-gnu/bin/ld: /tmp/build/perf/perf-in.o: in function `__parse_regs':
> /git/linux/tools/perf/util/parse-regs-options.c:39: undefined reference to `sample_reg_masks'
> /usr/lib/gcc-cross/aarch64-linux-gnu/8/../../../../aarch64-linux-gnu/bin/ld: /git/linux/tools/perf/util/parse-regs-options.c:47: undefined reference to `sample_reg_masks'
> /usr/lib/gcc-cross/aarch64-linux-gnu/8/../../../../aarch64-linux-gnu/bin/ld: /git/linux/tools/perf/util/parse-regs-options.c:60: undefined reference to `sample_reg_masks'
> /usr/lib/gcc-cross/aarch64-linux-gnu/8/../../../../aarch64-linux-gnu/bin/ld: /git/linux/tools/perf/util/parse-regs-options.c:50: undefined reference to `sample_reg_masks'

argh.. I tried on power.. should have tried on arm ;-)

I expected that all the archs that set NO_PERF_REGS := 0 would have
sample_reg_masks defined..  all those archs did fallback to the:

  const struct sample_reg __weak sample_reg_masks[] = {
       SMPL_REG_END
  };

those archs are not able to use --user-regs/--intr-regs options,
but for dwarf unwind we set those registers manualy, so that works

so I guess we need to define empty sample_reg_masks for those archs

jirka