Hello,
The commit that this patch is fixing[1] also causes yet another segfault for
'perf-script' of tracepoint records. For example:
$ sudo timeout 3 perf record -e exceptions:page_fault_user
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.228 MB perf.data (74 samples) ]
$ sudo perf script
Segmentation fault
Reverting this patch and the original bug commit[1] fixes the issue. I haven't
deep dive yet because I'm not familiar with this area. Anybody has any idea
about this?
[1] 838d9bb62d13 ("perf: Use sample_flags for raw_data")
Thanks,
SJ
On Fri, 7 Oct 2022 10:13:27 +0200 Sumanth Korikkar <sumanthk@xxxxxxxxxxxxx> wrote:
> * Raw data is also filled by bpf_perf_event_output.
> * Add sample_flags to indicate raw data.
> * This eliminates the segfaults as shown below:
> Run ./samples/bpf/trace_output
> BUG pid 9 cookie 1001000000004 sized 4
> BUG pid 9 cookie 1001000000004 sized 4
> BUG pid 9 cookie 1001000000004 sized 4
> Segmentation fault (core dumped)
>
> Fixes: 838d9bb62d13 ("perf: Use sample_flags for raw_data")
> Acked-by: Namhyung Kim <namhyung@xxxxxxxxxx>
> Signed-off-by: Sumanth Korikkar <sumanthk@xxxxxxxxxxxxx>
> ---
> kernel/trace/bpf_trace.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 49fb9ec8366d..1ed08967fb97 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -687,6 +687,7 @@ BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map,
>
> perf_sample_data_init(sd, 0, 0);
> sd->raw = &raw;
> + sd->sample_flags |= PERF_SAMPLE_RAW;
>
> err = __bpf_perf_event_output(regs, map, flags, sd);
>
> @@ -745,6 +746,7 @@ u64 bpf_event_output(struct bpf_map *map, u64 flags, void *meta, u64 meta_size,
> perf_fetch_caller_regs(regs);
> perf_sample_data_init(sd, 0, 0);
> sd->raw = &raw;
> + sd->sample_flags |= PERF_SAMPLE_RAW;
>
> ret = __bpf_perf_event_output(regs, map, flags, sd);
> out:
> --
> 2.36.1
