Merge branch 'bpf: Show target_{obj,btf}_id for tracing link'

Yafang Shao says:

====================
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.

For some other link types like perf_event and kprobe_multi, it is not
easy to find which functions are attached either. We may support
->fill_link_info for them in the future.

v1->v2:
- Skip showing them in the plain output for the old kernels. (Quentin)
- Coding improvement. (Andrii)
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c
index 243b74e18e51..2d786072ed0d 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 +377,10 @@ 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);
+		if (info->tracing.target_obj_id || info->tracing.target_btf_id)
+			printf("\n\ttarget_obj_id %u  target_btf_id %u  ",
+			       info->tracing.target_obj_id,
+			       info->tracing.target_btf_id);
 		break;
 	case BPF_LINK_TYPE_CGROUP:
 		printf("\n\tcgroup_id %zu  ", (size_t)info->cgroup.cgroup_id);