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References: <20240117215101.77713-1-ilkka@os.amperecomputing.com> <d77856e0-50e8-b7b4-734-93be3447ed73@os.amperecomputing.com>
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From: Namhyung Kim <namhyung@kernel.org>
Date: Thu, 22 Feb 2024 23:12:09 -0800
Message-ID: <CAM9d7cibn7ygfZoHCMNJF0DvRNw4dcyBHSbF0Jm20BaEoQbC=Q@mail.gmail.com>
Subject: Re: [PATCH v3] 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>, 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>, 
	Evgeny Pistun <kotborealis@awooo.ru>, linux-perf-users@vger.kernel.org, 
	linux-kernel@vger.kernel.org
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Hello,

On Thu, Feb 22, 2024 at 1:42=E2=80=AFPM Ilkka Koskinen
<ilkka@os.amperecomputing.com> wrote:
>
>
> cc: Evgeny Pistun since he submitted a patch pretty similar to my first
> version
> (https://lore.kernel.org/all/20240125184411.30757-1-kotborealis@awooo.ru/=
)
>
>
>
> Namhyung and James,
>
> What's your thought on this? Is one of the patches (Evgeny's or mine)
> good enough or should we try some other approach?

Sorry for the long delay.  Please see my comments below.

>
>
> On Wed, 17 Jan 2024, 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>
> > ---
> > v1:
> >    - https://lore.kernel.org/all/20240111232923.8138-1-ilkka@os.amperec=
omputing.com/
> > v2:
> >    - Changed the patch based on James's comments.
> > v3:
> >    - The architecture is checked from the actual data file to allow one=
 to do
> >      conversion on another system. (thanks to James for the feedback)
> > ---
> > tools/perf/util/data-convert-json.c | 8 +++++++-
> > 1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/util/data-convert-json.c b/tools/perf/util/data=
-convert-json.c
> > index 5bb3c2ba95ca..405c38371870 100644
> > --- a/tools/perf/util/data-convert-json.c
> > +++ b/tools/perf/util/data-convert-json.c
> > @@ -284,7 +284,13 @@ static void output_headers(struct perf_session *se=
ssion, struct convert_json *c)
> >       output_json_key_string(out, true, 2, "os-release", header->env.os=
_release);
> >       output_json_key_string(out, true, 2, "arch", header->env.arch);
> >
> > -     output_json_key_string(out, true, 2, "cpu-desc", header->env.cpu_=
desc);
> > +     /*
> > +      * Arm64 doesn't have Model section in /proc/cpuinfo and, thus, c=
pu-desc
> > +      * is not set.
> > +      */
> > +     if (strncmp(header->env.arch, "aarch64", 7))
> > +             output_json_key_string(out, true, 2, "cpu-desc", header->=
env.cpu_desc);

I prefer checking cpu_desc (if it's NULL) not the arch string.
Maybe other arch has the same problem or can introduce one later..

Thanks,
Namhyung

> > +
> >       output_json_key_string(out, true, 2, "cpuid", header->env.cpuid);
> >       output_json_key_format(out, true, 2, "nrcpus-online", "%u", heade=
r->env.nr_cpus_online);
> >       output_json_key_format(out, true, 2, "nrcpus-avail", "%u", header=
->env.nr_cpus_avail);
> > --
> > 2.43.0
> >
> >