linux-kernel - Re: [PATCH] tools/perf: Fix to get the DW_AT_decl_file and DW_AT_call

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Message-ID: <CAM9d7ci8YX22Bp31ZD9k31NFN6pP3fbPKpNDNZYnmdZiqav1Vg@mail.gmail.com>
Date:   Mon, 7 Nov 2022 13:09:00 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>, linux-perf-users@...r.kernel.org,
        linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] tools/perf: Fix to get the DW_AT_decl_file and
 DW_AT_call_file as unsinged data

Hi Masami,

On Fri, Nov 4, 2022 at 8:01 PM Masami Hiramatsu (Google)
<mhiramat@...nel.org> wrote:
>
> From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
>
> Dwarf version 5 standard Sec 2.14 says that
>
>   Any debugging information entry representing the declaration of an object,
>   module, subprogram or type may have DW_AT_decl_file, DW_AT_decl_line and
>   DW_AT_decl_column attributes, each of whose value is an unsigned integer
>   constant.
>
> So it should be an unsigned integer data. Also, even though the standard
> doesn't clearly say the DW_AT_call_file is signed or unsigned, the
> elfutils (eu-readelf) interprets it as unsigned integer data and it is
> natural to handle it as unsigned integer data as same as DW_AT_decl_file.
> This changes the DW_AT_call_file as unsigned integer data too.
>
> Fixes: 3f4460a28fb2 ("perf probe: Filter out redundant inline-instances")
> Cc: stable@...r.kernel.org
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Acked-by: Namhyung Kim <namhyung@...nel.org>

Thanks,
Namhyung


> ---
>  tools/perf/util/dwarf-aux.c |   21 ++++-----------------
>  1 file changed, 4 insertions(+), 17 deletions(-)
>
> diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
> index 30b36b525681..b07414409771 100644
> --- a/tools/perf/util/dwarf-aux.c
> +++ b/tools/perf/util/dwarf-aux.c
> @@ -315,19 +315,6 @@ static int die_get_attr_udata(Dwarf_Die *tp_die, unsigned int attr_name,
>         return 0;
>  }
>
> -/* Get attribute and translate it as a sdata */
> -static int die_get_attr_sdata(Dwarf_Die *tp_die, unsigned int attr_name,
> -                             Dwarf_Sword *result)
> -{
> -       Dwarf_Attribute attr;
> -
> -       if (dwarf_attr_integrate(tp_die, attr_name, &attr) == NULL ||
> -           dwarf_formsdata(&attr, result) != 0)
> -               return -ENOENT;
> -
> -       return 0;
> -}
> -
>  /**
>   * die_is_signed_type - Check whether a type DIE is signed or not
>   * @tp_die: a DIE of a type
> @@ -467,9 +454,9 @@ int die_get_data_member_location(Dwarf_Die *mb_die, Dwarf_Word *offs)
>  /* Get the call file index number in CU DIE */
>  static int die_get_call_fileno(Dwarf_Die *in_die)
>  {
> -       Dwarf_Sword idx;
> +       Dwarf_Word idx;
>
> -       if (die_get_attr_sdata(in_die, DW_AT_call_file, &idx) == 0)
> +       if (die_get_attr_udata(in_die, DW_AT_call_file, &idx) == 0)
>                 return (int)idx;
>         else
>                 return -ENOENT;
> @@ -478,9 +465,9 @@ static int die_get_call_fileno(Dwarf_Die *in_die)
>  /* Get the declared file index number in CU DIE */
>  static int die_get_decl_fileno(Dwarf_Die *pdie)
>  {
> -       Dwarf_Sword idx;
> +       Dwarf_Word idx;
>
> -       if (die_get_attr_sdata(pdie, DW_AT_decl_file, &idx) == 0)
> +       if (die_get_attr_udata(pdie, DW_AT_decl_file, &idx) == 0)
>                 return (int)idx;
>         else
>                 return -ENOENT;
>