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References: <20240111232923.8138-1-ilkka@os.amperecomputing.com> <2c9f5893-450c-012b-b748-a8fe8ddfae86@arm.com>
In-Reply-To: <2c9f5893-450c-012b-b748-a8fe8ddfae86@arm.com>
From: Namhyung Kim <namhyung@kernel.org>
Date: Tue, 16 Jan 2024 13:53:49 -0800
Message-ID: <CAM9d7ch5b9XHzQ-Hb=kPu-6jLyESWqgizz6MRNWb0d-NnK9aqg@mail.gmail.com>
Subject: Re: [PATCH] perf data convert: Fix segfault when converting to json
 on arm64
To: Ilkka Koskinen <ilkka@os.amperecomputing.com>
Cc: James Clark <james.clark@arm.com>, linux-perf-users@vger.kernel.org, 
	linux-kernel@vger.kernel.org, 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>, 
	Ian Rogers <irogers@google.com>, Adrian Hunter <adrian.hunter@intel.com>
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Hello,

On Fri, Jan 12, 2024 at 3:35=E2=80=AFAM James Clark <james.clark@arm.com> w=
rote:
>
>
>
> On 11/01/2024 23:29, Ilkka Koskinen wrote:
> > Arm64 doesn't have Model in /proc/cpuinfo and, thus, cpu_desc doesn't g=
et
> > assigned.
> >
> > Running
> >       $ perf data convert --to-json perf.data.json
> >
> > ends up calling output_json_string() with NULL pointer, which causes a
> > segmentation fault.
> >
> > Signed-off-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>
> > ---
> >  tools/perf/util/data-convert-json.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/tools/perf/util/data-convert-json.c b/tools/perf/util/data=
-convert-json.c
> > index 5bb3c2ba95ca..5d6de1cef546 100644
> > --- a/tools/perf/util/data-convert-json.c
> > +++ b/tools/perf/util/data-convert-json.c
> > @@ -97,6 +97,11 @@ static void output_json_format(FILE *out, bool comma=
, int depth, const char *for
> >  static void output_json_key_string(FILE *out, bool comma, int depth,
> >               const char *key, const char *value)
> >  {
> > +     if (!value) {
> > +             pr_info("No value set for key %s\n", key);
> > +             return;
> > +     }
> > +
> >       output_json_delimiters(out, comma, depth);
> >       output_json_string(out, key);
> >       fputs(": ", out);
>
>
> It looks like this would hide new errors on any of the other fields that
> output_json_key_string() is called on. Maybe it would be better to only
> wrap the call to output cpu_desc with the if? If that's the only one
> that we think is optional, and even better only do it for arm64.
>
> I mention this because the test for 'perf data convert' only checks for
> valid json syntax, but not any fields. So we might want to avoid others
> going missing.

Makes sense.  Ilkka, can you send v2 with this?

Thanks,
Namhyung