[RFC PATCH bpf-next 8/8] bpftool: Show probed function in perf_event link info

[Yafang Shao <laoar.shao@xxxxxxxxx>]

Show the exposed perf_event link info in bpftool. The result as follows,

$ bpftool link show
1: perf_event  prog 5
        func kernel_clone  addr ffffffffb40bc310  offset 0
        bpf_cookie 0
        pids trace(9726)
$ bpftool link show -j
[{"id":1,"type":"perf_event","prog_id":5,"func":"kernel_clone","addr":18446744072435254032,"offset":0,"bpf_cookie":0,"pids":[{"pid":9726,"comm":"trace"}]}]

Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
---
 tools/bpf/bpftool/link.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/tools/bpf/bpftool/link.c b/tools/bpf/bpftool/link.c
index 76f1bb2..8493a05 100644
--- a/tools/bpf/bpftool/link.c
+++ b/tools/bpf/bpftool/link.c
@@ -232,6 +232,12 @@ static int show_link_close_json(int fd, struct bpf_link_info *info)
 			jsonw_lluint(json_wtr, addrs[i]);
 		jsonw_end_array(json_wtr);
 		break;
+	case BPF_LINK_TYPE_PERF_EVENT:
+		jsonw_string_field(json_wtr, "func",
+				   u64_to_ptr(info->perf_event.name));
+		jsonw_uint_field(json_wtr, "addr", info->perf_event.addr);
+		jsonw_uint_field(json_wtr, "offset", info->perf_event.offset);
+		break;
 	default:
 		break;
 	}
@@ -368,7 +374,7 @@ void netfilter_dump_plain(const struct bpf_link_info *info)
 static int show_link_close_plain(int fd, struct bpf_link_info *info)
 {
 	struct bpf_prog_info prog_info;
-	const char *prog_type_str;
+	const char *prog_type_str, *buf;
 	int err;
 
 	show_link_header_plain(info);
@@ -428,6 +434,12 @@ static int show_link_close_plain(int fd, struct bpf_link_info *info)
 			printf(" %0*llx", 16, addrs[i]);
 		}
 		break;
+	case BPF_LINK_TYPE_PERF_EVENT:
+		buf = (const char *)u64_to_ptr(info->perf_event.name);
+		if (buf[0] != '\0' || info->perf_event.addr)
+			printf("\n\tfunc %s  addr %llx  offset %d  ", buf,
+			       info->perf_event.addr, info->perf_event.offset);
+		break;
 	default:
 		break;
 	}
@@ -454,6 +466,7 @@ static int do_show_link(int fd)
 	int count;
 	int err;
 
+	buf[0] = '\0';
 	memset(&info, 0, sizeof(info));
 again:
 	err = bpf_link_get_info_by_fd(fd, &info, &len);
@@ -489,6 +502,12 @@ static int do_show_link(int fd)
 			goto again;
 		}
 	}
+	if (info.type == BPF_LINK_TYPE_PERF_EVENT &&
+	    !info.perf_event.name) {
+		info.perf_event.name = (unsigned long)&buf;
+		info.perf_event.name_len = sizeof(buf);
+		goto again;
+	}
 
 	if (json_output)
 		show_link_close_json(fd, &info);
-- 
1.8.3.1