bpf: Add support for tracing_multi link fdinfo

Adding tracing_multi link fdinfo support with following output:

pos:    0
flags:  02000000
mnt_id: 19
ino:    3087
link_type:      tracing_multi
link_id:        9
prog_tag:       599ba0e317244f86
prog_id:        94
attach_type:    59
cnt:    10
obj-id   btf-id  cookie  func
1        91593   8       bpf_fentry_test1+0x4/0x10
1        91595   9       bpf_fentry_test2+0x4/0x10
1        91596   7       bpf_fentry_test3+0x4/0x20
1        91597   5       bpf_fentry_test4+0x4/0x20
1        91598   4       bpf_fentry_test5+0x4/0x20
1        91599   2       bpf_fentry_test6+0x4/0x20
1        91600   3       bpf_fentry_test7+0x4/0x10
1        91601   1       bpf_fentry_test8+0x4/0x10
1        91602   10      bpf_fentry_test9+0x4/0x10
1        91594   6       bpf_fentry_test10+0x4/0x10

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20260606123955.345967-17-jolsa@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index a0d688fffc5a580684457d125628072d8e3801c2..90432f0fc2a8eb281f09f0ac281d28320ee17e71 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -3665,9 +3665,39 @@ static void bpf_tracing_multi_link_dealloc(struct bpf_link *link)
        kvfree(tr_link);
 }
 
+#ifdef CONFIG_PROC_FS
+static void bpf_tracing_multi_show_fdinfo(const struct bpf_link *link,
+                                         struct seq_file *seq)
+{
+       struct bpf_tracing_multi_link *tr_link =
+               container_of(link, struct bpf_tracing_multi_link, link);
+       bool has_cookies = !!tr_link->cookies;
+
+       seq_printf(seq, "attach_type:\t%u\n", tr_link->link.attach_type);
+       seq_printf(seq, "cnt:\t%u\n", tr_link->nodes_cnt);
+
+       seq_printf(seq, "%s\t %s\t %s\t %s\n", "obj-id", "btf-id", "cookie", "func");
+       for (int i = 0; i < tr_link->nodes_cnt; i++) {
+               struct bpf_tracing_multi_node *mnode = &tr_link->nodes[i];
+               u32 btf_id, obj_id;
+
+               bpf_trampoline_unpack_key(mnode->trampoline->key, &obj_id, &btf_id);
+               seq_printf(seq, "%u\t %u\t %llu\t %pS\n",
+                          obj_id, btf_id,
+                          has_cookies ? tr_link->cookies[i] : 0,
+                          (void *) mnode->trampoline->ip);
+
+               cond_resched();
+       }
+}
+#endif
+
 static const struct bpf_link_ops bpf_tracing_multi_link_lops = {
        .release = bpf_tracing_multi_link_release,
        .dealloc_deferred = bpf_tracing_multi_link_dealloc,
+#ifdef CONFIG_PROC_FS
+       .show_fdinfo = bpf_tracing_multi_show_fdinfo,
+#endif
 };
 
 static int ids_cmp_r(const void *pa, const void *pb, const void *priv __maybe_unused)