On Thu, Feb 25, 2021 at 02:25:30PM +0800, Jackie Liu wrote:
> After install the libelf-dev package and compiling perf, kptr_restrict=2
> and perf_event_paranoid=3 will cause perf top to crash, because the
> value of /proc/kallsyms cannot be obtained, which leads to
> info->jited_ksyms == NULL. In order to solve this problem, Add a
> judgment before use.
>
> Suggested-by: Jiri Olsa <jo...@redhat.com>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Ingo Molnar <mi...@redhat.com>
> Cc: Arnaldo Carvalho de Melo <a...@kernel.org>
> Cc: Mark Rutland <mark.rutl...@arm.com>
> Cc: Alexander Shishkin <alexander.shish...@linux.intel.com>
> Cc: Namhyung Kim <namhy...@kernel.org>
> Signed-off-by: Jackie Liu <liuyu...@kylinos.cn>
> ---
> tools/perf/util/bpf-event.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/tools/perf/util/bpf-event.c b/tools/perf/util/bpf-event.c
> index 57d58c81a5f8..b1ce2d189d37 100644
> --- a/tools/perf/util/bpf-event.c
> +++ b/tools/perf/util/bpf-event.c
> @@ -225,6 +225,11 @@ static int perf_event__synthesize_one_bpf_prog(struct
> perf_session *session,
> perf_env__fetch_btf(env, info->btf_id, btf);
> }
>
> + if (!info->jited_ksyms) {
> + err = -1;
> + goto out;
> + }
> +
I think this check should be moved above, right after line:
info = &info_linear->info;
so we don't do those extra btf checks
thanks,
jirka
> /* Synthesize PERF_RECORD_KSYMBOL */
> for (i = 0; i < sub_prog_cnt; i++) {
> __u32 *prog_lens = (__u32 *)(uintptr_t)(info->jited_func_lens);
> --
> 2.25.1
>
