libbpf: Deprecate bpf_object__unload() API since v0.6

BPF objects are not reloadable after unload. Users are expected to use
bpf_object__close() to unload and free up resources in one operation.
No need to expose bpf_object__unload() as a public API, deprecate it
([0]).  Add bpf_object__unload() as an alias to internal
bpf_object_unload() and replace all bpf_object__unload() uses to avoid
compilation errors.

  [0] Closes: libbpf/libbpf#290

Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20211002161000.3854559-1-hengqi.chen@gmail.com

tools/lib/bpf/libbpf.c

@@ -6672,7 +6672,7 @@ bpf_object__open_buffer(const void *obj_buf, size_t obj_buf_sz,
 	return libbpf_ptr(__bpf_object__open(NULL, obj_buf, obj_buf_sz, &opts));
 }
 
-int bpf_object__unload(struct bpf_object *obj)
+static int bpf_object_unload(struct bpf_object *obj)
 {
 	size_t i;
 
@@ -6691,6 +6691,8 @@ int bpf_object__unload(struct bpf_object *obj)
 	return 0;
 }
 
+int bpf_object__unload(struct bpf_object *obj) __attribute__((alias("bpf_object_unload")));
+
 static int bpf_object__sanitize_maps(struct bpf_object *obj)
 {
 	struct bpf_map *m;
@@ -7089,7 +7091,7 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
 		if (obj->maps[i].pinned && !obj->maps[i].reused)
 			bpf_map__unpin(&obj->maps[i], NULL);
 
-	bpf_object__unload(obj);
+	bpf_object_unload(obj);
 	pr_warn("failed to load object '%s'\n", obj->path);
 	return libbpf_err(err);
 }
@@ -7698,7 +7700,7 @@ void bpf_object__close(struct bpf_object *obj)
 
 	bpf_gen__free(obj->gen_loader);
 	bpf_object__elf_finish(obj);
-	bpf_object__unload(obj);
+	bpf_object_unload(obj);
 	btf__free(obj->btf);
 	btf_ext__free(obj->btf_ext);
 

tools/lib/bpf/libbpf.h

@@ -150,6 +150,7 @@ struct bpf_object_load_attr {
 /* Load/unload object into/from kernel */
 LIBBPF_API int bpf_object__load(struct bpf_object *obj);
 LIBBPF_API int bpf_object__load_xattr(struct bpf_object_load_attr *attr);
+LIBBPF_DEPRECATED_SINCE(0, 6, "bpf_object__unload() is deprecated, use bpf_object__close() instead")
 LIBBPF_API int bpf_object__unload(struct bpf_object *obj);
 
 LIBBPF_API const char *bpf_object__name(const struct bpf_object *obj);