Re: [PATCH] [PING] perf ftrace: Command fails on s390

[Namhyung Kim]

Hello,

On Wed, Apr 21, 2021 at 10:03 PM Thomas Richter <tmricht@xxxxxxxxxxxxx> wrote:
>
> Command 'perf ftrace -v -- ls' fails in s390 (at least 5.12.0rc6).
>
> The root cause is a missing pointer dereference which causes an
> array element address to be used as PID.
>
> Fix this by extracting the PID.
>
> Output before:
>   # ./perf ftrace -v -- ls
>   function_graph tracer is used
>   write '-263732416' to tracing/set_ftrace_pid failed: Invalid argument
>   failed to set ftrace pid
>   #
>
> Output after:
>    ./perf ftrace -v -- ls
>    function_graph tracer is used
>    # tracer: function_graph
>    #
>    # CPU  DURATION                  FUNCTION CALLS
>    # |     |   |                     |   |   |   |
>    4)               |  rcu_read_lock_sched_held() {
>    4)   0.552 us    |    rcu_lockdep_current_cpu_online();
>    4)   6.124 us    |  }
>
> Signed-off-by: Thomas Richter <tmricht@xxxxxxxxxxxxx>
> Reported-by: Alexander Schmidt <alexschm@xxxxxxxxxx>

Acked-by: Namhyung Kim <namhyung@xxxxxxxxxx>

Thanks,
Namhyung

> ---
>  tools/perf/builtin-ftrace.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
> index d49448a1060c..87cb11a7a3ee 100644
> --- a/tools/perf/builtin-ftrace.c
> +++ b/tools/perf/builtin-ftrace.c
> @@ -289,7 +289,7 @@ static int set_tracing_pid(struct perf_ftrace *ftrace)
>
>         for (i = 0; i < perf_thread_map__nr(ftrace->evlist->core.threads); i++) {
>                 scnprintf(buf, sizeof(buf), "%d",
> -                         ftrace->evlist->core.threads->map[i]);
> +                         perf_thread_map__pid(ftrace->evlist->core.threads, i));
>                 if (append_tracing_file("set_ftrace_pid", buf) < 0)
>                         return -1;
>         }
> --
> 2.30.2
>