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From:   Namhyung Kim <namhyung@kernel.org>
Date:   Sun, 8 Oct 2023 23:21:03 -0700
Message-ID: <CAM9d7cj3AuAo-+ncd6nULusvgw1NUhBdSAED9vf_eDQ7Z=cEPQ@mail.gmail.com>
Subject: Re: [PATCH v2 10/18] perf dlfilter: Be defensive against potential
 NULL dereference
To:     Ian Rogers <irogers@google.com>
Cc:     Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Tom Rix <trix@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Yicong Yang <yangyicong@hisilicon.com>,
        Jonathan Cameron <jonathan.cameron@huawei.com>,
        Yang Jihong <yangjihong1@huawei.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        Ming Wang <wangming01@loongson.cn>,
        Huacai Chen <chenhuacai@kernel.org>,
        Sean Christopherson <seanjc@google.com>,
        K Prateek Nayak <kprateek.nayak@amd.com>,
        Yanteng Si <siyanteng@loongson.cn>,
        Yuan Can <yuancan@huawei.com>,
        Ravi Bangoria <ravi.bangoria@amd.com>,
        James Clark <james.clark@arm.com>, llvm@lists.linux.dev,
        linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        bpf@vger.kernel.org
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On Thu, Oct 5, 2023 at 4:09 PM Ian Rogers <irogers@google.com> wrote:
>
> In the unlikely case of having a symbol without a mapping, avoid a
> NULL dereference that clang-tidy warns about.

I'm not sure if it's possible to have a symbol without a map,
but I'm also fine with being conservative.

Thanks,
Namhyung

>
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/perf/util/dlfilter.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/tools/perf/util/dlfilter.c b/tools/perf/util/dlfilter.c
> index 1dbf27822ee2..5e54832137a9 100644
> --- a/tools/perf/util/dlfilter.c
> +++ b/tools/perf/util/dlfilter.c
> @@ -52,8 +52,10 @@ static void al_to_d_al(struct addr_location *al, struct perf_dlfilter_al *d_al)
>                 d_al->sym_end = sym->end;
>                 if (al->addr < sym->end)
>                         d_al->symoff = al->addr - sym->start;
> -               else
> +               else if (al->map)
>                         d_al->symoff = al->addr - map__start(al->map) - sym->start;
> +               else
> +                       d_al->symoff = 0;
>                 d_al->sym_binding = sym->binding;
>         } else {
>                 d_al->sym = NULL;
> --
> 2.42.0.609.gbb76f46606-goog
>