[PATCH bpf-next v8 5/5] bpftool: Show parameters of BPF task iterators.

[Kui-Feng Lee <kuifeng@xxxxxx>]

Show tid or pid of iterators if giving an argument of tid or pid

For example, the command `bpftool link list` may list following
lines.

1: iter  prog 2  target_name bpf_map
2: iter  prog 3  target_name bpf_prog
33: iter  prog 225  target_name task_file  tid 1644
        pids test_progs(1644)

Link 33 is a task_file iterator with tid 1644.  For now, only targets
of task, task_file and task_vma may be with tid or pid to filter out
tasks other than those belonging to a process (pid) or a thread (tid).

Signed-off-by: Kui-Feng Lee <kuifeng@xxxxxx>
---
 tools/bpf/bpftool/link.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c
index 7a20931c3250..88937036fae0 100644
--- a/tools/bpf/bpftool/link.c
+++ b/tools/bpf/bpftool/link.c
@@ -83,6 +83,13 @@ static bool is_iter_map_target(const char *target_name)
 	       strcmp(target_name, "bpf_sk_storage_map") == 0;
 }
 
+static bool is_iter_task_target(const char *target_name)
+{
+	return strcmp(target_name, "task") == 0 ||
+		strcmp(target_name, "task_file") == 0 ||
+		strcmp(target_name, "task_vma") == 0;
+}
+
 static void show_iter_json(struct bpf_link_info *info, json_writer_t *wtr)
 {
 	const char *target_name = u64_to_ptr(info->iter.target_name);
@@ -91,6 +98,12 @@ static void show_iter_json(struct bpf_link_info *info, json_writer_t *wtr)
 
 	if (is_iter_map_target(target_name))
 		jsonw_uint_field(wtr, "map_id", info->iter.map.map_id);
+	else if (is_iter_task_target(target_name)) {
+		if (info->iter.task.tid)
+			jsonw_uint_field(wtr, "tid", info->iter.task.tid);
+		else if (info->iter.task.pid)
+			jsonw_uint_field(wtr, "pid", info->iter.task.pid);
+	}
 }
 
 static int get_prog_info(int prog_id, struct bpf_prog_info *info)
@@ -208,6 +221,12 @@ static void show_iter_plain(struct bpf_link_info *info)
 
 	if (is_iter_map_target(target_name))
 		printf("map_id %u  ", info->iter.map.map_id);
+	else if (is_iter_task_target(target_name)) {
+		if (info->iter.task.tid)
+			printf("tid %u ", info->iter.task.tid);
+		else if (info->iter.task.pid)
+			printf("pid %u ", info->iter.task.pid);
+	}
 }
 
 static int show_link_close_plain(int fd, struct bpf_link_info *info)
-- 
2.30.2