[PATCH RFC bpf-next 3/4] libbpf: Add return_prog_fd to kprobe multi opts

[Jiri Olsa <jolsa@kernel.org>]

Adding support to specify return prog file descriptor in struct
bpf_kprobe_multi_opts.

When the return_prog bool is set true the return_prog_fd is used
as bpf program to be executed for the return probe.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 tools/lib/bpf/bpf.c    | 1 +
 tools/lib/bpf/bpf.h    | 1 +
 tools/lib/bpf/libbpf.c | 5 +++++
 tools/lib/bpf/libbpf.h | 6 +++++-
 4 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 97ec005c3c47..9f296957bd30 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -771,6 +771,7 @@ int bpf_link_create(int prog_fd, int target_fd,
 		attr.link_create.kprobe_multi.syms = ptr_to_u64(OPTS_GET(opts, kprobe_multi.syms, 0));
 		attr.link_create.kprobe_multi.addrs = ptr_to_u64(OPTS_GET(opts, kprobe_multi.addrs, 0));
 		attr.link_create.kprobe_multi.cookies = ptr_to_u64(OPTS_GET(opts, kprobe_multi.cookies, 0));
+		attr.link_create.kprobe_multi.return_prog_fd = OPTS_GET(opts, kprobe_multi.return_prog_fd, 0);
 		if (!OPTS_ZEROED(opts, kprobe_multi))
 			return libbpf_err(-EINVAL);
 		break;
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index f866e98b2436..e04a14134a21 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -399,6 +399,7 @@ struct bpf_link_create_opts {
 			const char **syms;
 			const unsigned long *addrs;
 			const __u64 *cookies;
+			__u32 return_prog_fd;
 		} kprobe_multi;
 		struct {
 			__u32 flags;
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 01f407591a92..022a68b9fe83 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -11073,6 +11073,11 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
 	lopts.kprobe_multi.cnt = cnt;
 	lopts.kprobe_multi.flags = retprobe ? BPF_F_KPROBE_MULTI_RETURN : 0;
 
+	if (OPTS_GET(opts, return_prog, false)) {
+		lopts.kprobe_multi.return_prog_fd = OPTS_GET(opts, return_prog_fd, 0);
+		lopts.kprobe_multi.flags |= BPF_F_KPROBE_MULTI_RETURN_PROG;
+	}
+
 	link = calloc(1, sizeof(*link));
 	if (!link) {
 		err = -ENOMEM;
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 5723cbbfcc41..d77b953009d6 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -539,10 +539,14 @@ struct bpf_kprobe_multi_opts {
 	size_t cnt;
 	/* create return kprobes */
 	bool retprobe;
+	/* attach return program (specified by return_prog_fd file descriptor) */
+	bool return_prog;
+	/* return program fd */
+	int return_prog_fd;
 	size_t :0;
 };
 
-#define bpf_kprobe_multi_opts__last_field retprobe
+#define bpf_kprobe_multi_opts__last_field return_prog_fd
 
 LIBBPF_API struct bpf_link *
 bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
-- 
2.43.0