[PATCH bpf-next 1/2] bpf, libbpf: add a new API bpf_object__reuse_maps()

[Anton Protopopov <a.s.protopopov@xxxxxxxxx>]

Add a new API bpf_object__reuse_maps() which can be used to replace all maps in
an object by maps pinned to a directory provided in the path argument.  Namely,
each map M in the object will be replaced by a map pinned to path/M.name.

Signed-off-by: Anton Protopopov <a.s.protopopov@xxxxxxxxx>
---
 tools/lib/bpf/libbpf.c   | 34 ++++++++++++++++++++++++++++++++++
 tools/lib/bpf/libbpf.h   |  2 ++
 tools/lib/bpf/libbpf.map |  1 +
 3 files changed, 37 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 4907997289e9..84c9e8f7bfd3 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3144,6 +3144,40 @@ int bpf_object__unpin_maps(struct bpf_object *obj, const char *path)
 	return 0;
 }
 
+int bpf_object__reuse_maps(struct bpf_object *obj, const char *path)
+{
+	struct bpf_map *map;
+
+	if (!obj)
+		return -ENOENT;
+
+	if (!path)
+		return -EINVAL;
+
+	bpf_object__for_each_map(map, obj) {
+		int len, err;
+		int pinned_map_fd;
+		char buf[PATH_MAX];
+
+		len = snprintf(buf, PATH_MAX, "%s/%s", path, bpf_map__name(map));
+		if (len < 0) {
+			return -EINVAL;
+		} else if (len >= PATH_MAX) {
+			return -ENAMETOOLONG;
+		}
+
+		pinned_map_fd = bpf_obj_get(buf);
+		if (pinned_map_fd < 0)
+			return pinned_map_fd;
+
+		err = bpf_map__reuse_fd(map, pinned_map_fd);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
 int bpf_object__pin_programs(struct bpf_object *obj, const char *path)
 {
 	struct bpf_program *prog;
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index d639f47e3110..7fe465a1be76 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -82,6 +82,8 @@ int bpf_object__variable_offset(const struct bpf_object *obj, const char *name,
 LIBBPF_API int bpf_object__pin_maps(struct bpf_object *obj, const char *path);
 LIBBPF_API int bpf_object__unpin_maps(struct bpf_object *obj,
 				      const char *path);
+LIBBPF_API int bpf_object__reuse_maps(struct bpf_object *obj,
+				      const char *path);
 LIBBPF_API int bpf_object__pin_programs(struct bpf_object *obj,
 					const char *path);
 LIBBPF_API int bpf_object__unpin_programs(struct bpf_object *obj,
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 2c6d835620d2..66a30be6696c 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -172,5 +172,6 @@ LIBBPF_0.0.4 {
 		btf_dump__new;
 		btf__parse_elf;
 		bpf_object__load_xattr;
+		bpf_object__reuse_maps;
 		libbpf_num_possible_cpus;
 } LIBBPF_0.0.3;
-- 
2.19.1