On Tue, May 16, 2023 at 9:01 PM Quentin Monnet <quentin@xxxxxxxxxxxxx> wrote:
>
> 2023-05-16 12:39 UTC+0000 ~ Yafang Shao <laoar.shao@xxxxxxxxx>
> > The target_btf_id can help us understand which kernel function is
> > linked by a tracing prog. The target_btf_id and target_obj_id have
> > already been exposed to userspace, so we just need to show them.
> >
> > The result as follows,
> >
> > $ tools/bpf/bpftool/bpftool link show
> > 2: tracing prog 13
> > prog_type tracing attach_type trace_fentry
> > target_obj_id 1 target_btf_id 13964
> > pids trace(10673)
> >
> > $ tools/bpf/bpftool/bpftool link show -j
> > [{"id":2,"type":"tracing","prog_id":13,"prog_type":"tracing","attach_type":"trace_fentry","target_obj_id":1,"target_btf_id":13964,"pids":[{"pid":10673,"comm":"trace"}]}]
> >
> > Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> > Acked-by: Song Liu <song@xxxxxxxxxx>
> > ---
> > tools/bpf/bpftool/link.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c
> > index 243b74e..cfe896f 100644
> > --- a/tools/bpf/bpftool/link.c
> > +++ b/tools/bpf/bpftool/link.c
> > @@ -195,6 +195,8 @@ static int show_link_close_json(int fd, struct bpf_link_info *info)
> >
> > show_link_attach_type_json(info->tracing.attach_type,
> > json_wtr);
> > + jsonw_uint_field(json_wtr, "target_obj_id", info->tracing.target_obj_id);
> > + jsonw_uint_field(json_wtr, "target_btf_id", info->tracing.target_btf_id);
> > break;
> > case BPF_LINK_TYPE_CGROUP:
> > jsonw_lluint_field(json_wtr, "cgroup_id",
> > @@ -375,6 +377,8 @@ static int show_link_close_plain(int fd, struct bpf_link_info *info)
> > printf("\n\tprog_type %u ", prog_info.type);
> >
> > show_link_attach_type_plain(info->tracing.attach_type);
> > + printf("\n\ttarget_obj_id %u target_btf_id %u ",
> > + info->tracing.target_obj_id, info->tracing.target_btf_id);
>
> Older kernels won't share this info, so maybe we can skip this printf()
> in plain output if the target object and BTF ids are 0?
>
Good suggestion. Will change it in the next version.
BTW, shouldn't we skip it in the json output as well ?
--
Regards
Yafang
