tools/bpf: bpftool: add btf percpu map formated dump

The btf pretty print is added to percpu arraymap,
percpu hashmap and percpu lru hashmap.
For each <key, value> pair, the following will be
added to plain/json output:

   {
       "key": <pretty_print_key>,
       "values": [{
             "cpu": 0,
             "value": <pretty_print_value_on_cpu0>
          },{
             "cpu": 1,
             "value": <pretty_print_value_on_cpu1>
          },{
          ....
          },{
             "cpu": n,
             "value": <pretty_print_value_on_cpun>
          }
       ]
   }

For example, the following could be part of plain or json formatted
output:
    {
        "key": 0,
        "values": [{
                "cpu": 0,
                "value": {
                    "ui32": 0,
                    "ui16": 0,
                }
            },{
                "cpu": 1,
                "value": {
                    "ui32": 1,
                    "ui16": 0,
                }
            },{
                "cpu": 2,
                "value": {
                    "ui32": 2,
                    "ui16": 0,
                }
            },{
                "cpu": 3,
                "value": {
                    "ui32": 3,
                    "ui16": 0,
                }
            }
        ]
    }
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/bpf/bpftool/map.c

@@ -169,9 +169,28 @@ static int do_dump_btf(const struct btf_dumper *d,
 	if (ret)
 		goto err_end_obj;
 
-	jsonw_name(d->jw, "value");
+	if (!map_is_per_cpu(map_info->type)) {
+		jsonw_name(d->jw, "value");
+		ret = btf_dumper_type(d, map_info->btf_value_type_id, value);
+	} else {
+		unsigned int i, n, step;
 
-	ret = btf_dumper_type(d, map_info->btf_value_type_id, value);
+		jsonw_name(d->jw, "values");
+		jsonw_start_array(d->jw);
+		n = get_possible_cpus();
+		step = round_up(map_info->value_size, 8);
+		for (i = 0; i < n; i++) {
+			jsonw_start_object(d->jw);
+			jsonw_int_field(d->jw, "cpu", i);
+			jsonw_name(d->jw, "value");
+			ret = btf_dumper_type(d, map_info->btf_value_type_id,
+					      value + i * step);
+			jsonw_end_object(d->jw);
+			if (ret)
+				break;
+		}
+		jsonw_end_array(d->jw);
+	}
 
 err_end_obj:
 	/* end of key-value pair */
@@ -298,6 +317,16 @@ static void print_entry_json(struct bpf_map_info *info, unsigned char *key,
 			jsonw_end_object(json_wtr);
 		}
 		jsonw_end_array(json_wtr);
+		if (btf) {
+			struct btf_dumper d = {
+				.btf = btf,
+				.jw = json_wtr,
+				.is_plain_text = false,
+			};
+
+			jsonw_name(json_wtr, "formatted");
+			do_dump_btf(&d, info, key, value);
+		}
 	}
 
 	jsonw_end_object(json_wtr);