From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Like Xu <like.xu.linux@gmail.com>
Cc: Ian Rogers <irogers@google.com>,
Alexander Antonov <alexander.antonov@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Namhyung Kim <namhyung@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Stephane Eranian <eranian@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] perf iostat: Fix Segmentation fault from NULL 'struct perf_counts_values *'
Date: Mon, 27 Sep 2021 09:42:44 -0300 [thread overview]
Message-ID: <YVG8RM+ofI25Rk2r@kernel.org> (raw)
In-Reply-To: <20210927081115.39568-2-likexu@tencent.com>
Em Mon, Sep 27, 2021 at 04:11:15PM +0800, Like Xu escreveu:
> From: Like Xu <likexu@tencent.com>
>
> If the perf-iostat user specifies two or more iio_root_ports and
> also specifies the cpu(s) by -C which is not *connected to all*
> the above iio ports, the iostat_print_metric() will run into trouble:
>
> For example:
>
> $ perf iostat list
> S0-uncore_iio_0<0000:16>
> S1-uncore_iio_0<0000:97> # <--- CPU 1 is located in the socket S0
>
> $ perf iostat 0000:16,0000:97 -C 1 -- ls
> port Inbound Read(MB) Inbound Write(MB) Outbound Read(MB) Outbound
> Write(MB) ../perf-iostat: line 12: 104418 Segmentation fault
> (core dumped) perf stat --iostat$DELIMITER$*
>
> The core-dump stack says, in the above corner case, the returned
> (struct perf_counts_values *) count will be NULL, and the caller
> iostat_print_metric() apparently doesn't not handle this case.
>
> 433 struct perf_counts_values *count = perf_counts(evsel->counts, die, 0);
> 434
> 435 if (count->run && count->ena) {
> (gdb) p count
> $1 = (struct perf_counts_values *) 0x0
>
> The deeper reason is that there are actually no statistics from the user
> specified pair "iostat 0000:X, -C (disconnected) Y ", but let's fix it with
> minimum cost by adding a NULL check in the user space.
Added:
Fixes: f9ed693e8bc0e7de ("perf stat: Enable iostat mode for x86 platforms")
Please do that next time,
- Arnaldo
> Signed-off-by: Like Xu <likexu@tencent.com>
> ---
> tools/perf/arch/x86/util/iostat.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/arch/x86/util/iostat.c b/tools/perf/arch/x86/util/iostat.c
> index eeafe97b8105..792cd75ade33 100644
> --- a/tools/perf/arch/x86/util/iostat.c
> +++ b/tools/perf/arch/x86/util/iostat.c
> @@ -432,7 +432,7 @@ void iostat_print_metric(struct perf_stat_config *config, struct evsel *evsel,
> u8 die = ((struct iio_root_port *)evsel->priv)->die;
> struct perf_counts_values *count = perf_counts(evsel->counts, die, 0);
>
> - if (count->run && count->ena) {
> + if (count && count->run && count->ena) {
> if (evsel->prev_raw_counts && !out->force_header) {
> struct perf_counts_values *prev_count =
> perf_counts(evsel->prev_raw_counts, die, 0);
> --
> 2.32.0
--
- Arnaldo
next prev parent reply other threads:[~2021-09-27 12:42 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-27 8:11 [PATCH 1/2] perf iostat: Use system-wide mode if the target cpu_list is unspecified Like Xu
2021-09-27 8:11 ` [PATCH 2/2] perf iostat: Fix Segmentation fault from NULL 'struct perf_counts_values *' Like Xu
2021-09-27 12:42 ` Arnaldo Carvalho de Melo [this message]
2021-09-27 12:40 ` [PATCH 1/2] perf iostat: Use system-wide mode if the target cpu_list is unspecified Arnaldo Carvalho de Melo
2021-09-28 9:06 ` Alexander Antonov
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