[PATCH bpf-next 2/2] bpf: Add show_fdinfo for kprobe_multi

[Tao Chen <chen.dylane@linux.dev>]

Show kprobe_multi link info with fdinfo, the info as follows:

link_type:	kprobe_multi
link_id:	4
prog_tag:	279dd9c09dfbc757
prog_id:	30
type:	kprobe_multi
func_cnt:	8
missed:	0
addr:	0xffffffff81ecb1e0
cookie:	8
addr:	0xffffffff81eccb70
cookie:	2
addr:	0xffffffff81eccba0
cookie:	7
addr:	0xffffffff81eccbd0
cookie:	6
addr:	0xffffffff81eccc00
cookie:	5
addr:	0xffffffff81eccc30
cookie:	4
addr:	0xffffffff81eccc60
cookie:	3
addr:	0xffffffff81eccc90
cookie:	1

Signed-off-by: Tao Chen <chen.dylane@linux.dev>
---
 kernel/trace/bpf_trace.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index c4ad82b8fd8..6c3ffa3c1ca 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2623,10 +2623,41 @@ static int bpf_kprobe_multi_link_fill_link_info(const struct bpf_link *link,
 	return err;
 }
 
+#ifdef CONFIG_PROC_FS
+static void bpf_kprobe_multi_show_fdinfo(const struct bpf_link *link,
+					 struct seq_file *seq)
+{
+	struct bpf_kprobe_multi_link *kmulti_link;
+
+	kmulti_link = container_of(link, struct bpf_kprobe_multi_link, link);
+
+	seq_printf(seq,
+		   "type:\t%s\n"
+		   "func_cnt:\t%u\n"
+		   "missed:\t%lu\n",
+		   kmulti_link->flags == BPF_F_KPROBE_MULTI_RETURN ? "kretprobe_multi" :
+					 "kprobe_multi",
+		   kmulti_link->cnt,
+		   kmulti_link->fp.nmissed);
+
+	for (int i = 0; i < kmulti_link->cnt; i++) {
+		seq_printf(seq,
+			  "addr:\t%#lx\n"
+			  "cookie:\t%llu\n",
+			  kmulti_link->addrs[i],
+			  kmulti_link->cookies[i]
+			  );
+	}
+}
+#endif
+
 static const struct bpf_link_ops bpf_kprobe_multi_link_lops = {
 	.release = bpf_kprobe_multi_link_release,
 	.dealloc_deferred = bpf_kprobe_multi_link_dealloc,
 	.fill_link_info = bpf_kprobe_multi_link_fill_link_info,
+#ifdef CONFIG_PROC_FS
+	.show_fdinfo = bpf_kprobe_multi_show_fdinfo,
+#endif
 };
 
 static void bpf_kprobe_multi_cookie_swap(void *a, void *b, int size, const void *priv)
-- 
2.48.1