[PATCH bpf-next v3 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:	1
prog_tag:	a15b7646cb7f3322
prog_id:	21
type:	kprobe_multi
kprobe_cnt:	8
missed:	0
cookie           func
1                bpf_fentry_test1
7                bpf_fentry_test2
2                bpf_fentry_test3
3                bpf_fentry_test4
4                bpf_fentry_test5
5                bpf_fentry_test6
6                bpf_fentry_test7
8                bpf_fentry_test8

Signed-off-by: Tao Chen <chen.dylane@linux.dev>
---
 kernel/trace/bpf_trace.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 2d422f897ac..fcf19e233b5 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2623,10 +2623,42 @@ 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;
+	char sym[KSYM_NAME_LEN];
+
+	kmulti_link = container_of(link, struct bpf_kprobe_multi_link, link);
+
+	seq_printf(seq,
+		   "type:\t%s\n"
+		   "kprobe_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);
+
+	seq_printf(seq, "%-16s %-16s\n", "cookie", "func");
+	for (int i = 0; i < kmulti_link->cnt; i++) {
+		sprint_symbol_no_offset(sym, kmulti_link->addrs[i]);
+		seq_printf(seq,
+			   "%-16llu %-16s\n",
+			   kmulti_link->cookies[i],
+			   sym);
+	}
+}
+#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