[PATCH bpf-next 2/2] bpf, libbpf: add an option to reuse existing maps in bpf_prog_load_xattr

[Anton Protopopov]

Add a new pinned_maps_path member to the bpf_prog_load_attr structure and
extend the bpf_prog_load_xattr() function to pass this pointer to the new
bpf_object__reuse_maps() helper. This change provides users with a simple
way to use existing pinned maps when (re)loading BPF programs.

Signed-off-by: Anton Protopopov <a.s.protopopov@xxxxxxxxx>
---
 tools/lib/bpf/libbpf.c | 8 ++++++++
 tools/lib/bpf/libbpf.h | 1 +
 2 files changed, 9 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 84c9e8f7bfd3..9daa09c9fe1a 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3953,6 +3953,14 @@ int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
 			first_prog = prog;
 	}
 
+	if (attr->pinned_maps_path) {
+		err = bpf_object__reuse_maps(obj, attr->pinned_maps_path);
+		if (err < 0) {
+			bpf_object__close(obj);
+			return err;
+		}
+	}
+
 	bpf_object__for_each_map(map, obj) {
 		if (!bpf_map__is_offload_neutral(map))
 			map->map_ifindex = attr->ifindex;
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 7fe465a1be76..6bf405bb9c1f 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -329,6 +329,7 @@ struct bpf_prog_load_attr {
 	int ifindex;
 	int log_level;
 	int prog_flags;
+	const char *pinned_maps_path;
 };
 
 LIBBPF_API int bpf_prog_load_xattr(const struct bpf_prog_load_attr *attr,
-- 
2.19.1