[PATCH] libbpf: kprobe.multi: feedback function counts by kernel traced

[Jackie Liu <liu.yun@linux.dev>]

From: Jackie Liu <liuyun01@kylinos.cn>

When tracking functions through kprobe.multi, the number of tracked
functions cannot be directly obtained. Sometimes in order to calculate
this value, it is necessary to recalculate according to the pattern in
the program. This is unnecessary. It is calculated by libbpf feedback
through opts.cnt value, which can save resources. Example at [1].

[1] https://github.com/JackieLiu1/ketones/blob/master/src/funccount/funccount.c#L317

Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
---
 tools/lib/bpf/libbpf.c | 3 ++-
 tools/lib/bpf/libbpf.h | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index fca5d2e412c5..ed3f1202c570 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -10506,7 +10506,7 @@ static void kprobe_multi_resolve_reinit(struct kprobe_multi_resolve *res)
 struct bpf_link *
 bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
 				      const char *pattern,
-				      const struct bpf_kprobe_multi_opts *opts)
+				      struct bpf_kprobe_multi_opts *opts)
 {
 	LIBBPF_OPTS(bpf_link_create_opts, lopts);
 	struct kprobe_multi_resolve res = {
@@ -10582,6 +10582,7 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
 	}
 	link->fd = link_fd;
 	free(res.addrs);
+	OPTS_SET(opts, cnt, res.cnt);
 	return link;
 
 error:
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 0b7362397ea3..f860dacc6add 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -527,7 +527,7 @@ struct bpf_kprobe_multi_opts {
 LIBBPF_API struct bpf_link *
 bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
 				      const char *pattern,
-				      const struct bpf_kprobe_multi_opts *opts);
+				      struct bpf_kprobe_multi_opts *opts);
 
 struct bpf_ksyscall_opts {
 	/* size of this struct, for forward/backward compatibility */
-- 
2.25.1