bpftool: Display cookie for tracing link probe

Display cookie for tracing link probe, in plain mode:

 #bpftool link
5: tracing  prog 34
	prog_type tracing  attach_type trace_fentry
	target_obj_id 1  target_btf_id 60355
	cookie 4503599627370496
	pids test_progs(176)

And in json mode:

 #bpftool link -j | jq
{
    "id": 5,
    "type": "tracing",
    "prog_id": 34,
    "prog_type": "tracing",
    "attach_type": "trace_fentry",
    "target_obj_id": 1,
    "target_btf_id": 60355,
    "cookie": 4503599627370496,
    "pids": [
      {
        "pid": 176,
        "comm": "test_progs"
      }
    ]
 }

Signed-off-by: Tao Chen <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

Author: Tao Chen

tools/bpf/bpftool/link.c

@@ -503,6 +503,7 @@ static int show_link_close_json(int fd, struct bpf_link_info *info)
 					   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);
+		jsonw_uint_field(json_wtr, "cookie", info->tracing.cookie);
 		break;
 	case BPF_LINK_TYPE_CGROUP:
 		jsonw_lluint_field(json_wtr, "cgroup_id",
@@ -900,6 +901,8 @@ static int show_link_close_plain(int fd, struct bpf_link_info *info)
 			printf("\n\ttarget_obj_id %u  target_btf_id %u  ",
 			       info->tracing.target_obj_id,
 			       info->tracing.target_btf_id);
+		if (info->tracing.cookie)
+			printf("\n\tcookie %llu  ", info->tracing.cookie);
 		break;
 	case BPF_LINK_TYPE_CGROUP:
 		printf("\n\tcgroup_id %zu  ", (size_t)info->cgroup.cgroup_id);