libbpf: Add split BTF support for btf__load_from_kernel_by_id()

mainline inclusion
from mainline-5.15-rc1
commit 61fc51b1
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=61fc51b1d3e5915e356f2c0b67cd3bb13b640413

-------------------------------------------------

Add a new API function btf__load_from_kernel_by_id_split(), which takes
a pointer to a base BTF object in order to support split BTF objects
when retrieving BTF information from the kernel.

Reference: https://github.com/libbpf/libbpf/issues/314Signed-off-by: NQuentin Monnet <quentin@isovalent.com>
Signed-off-by: NAndrii Nakryiko <andrii@kernel.org>
Acked-by: NJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210729162028.29512-8-quentin@isovalent.com
(cherry picked from commit 61fc51b1)
Signed-off-by: NWang Yufen <wangyufen@huawei.com>

tools/lib/bpf/btf.c

@@ -1388,7 +1388,7 @@ struct btf *btf_get_from_fd(int btf_fd, struct btf *base_btf)
 	return btf;
 }
 
-struct btf *btf__load_from_kernel_by_id(__u32 id)
+struct btf *btf__load_from_kernel_by_id_split(__u32 id, struct btf *base_btf)
 {
 	struct btf *btf;
 	int btf_fd;
@@ -1397,12 +1397,17 @@ struct btf *btf__load_from_kernel_by_id(__u32 id)
 	if (btf_fd < 0)
 		return libbpf_err_ptr(-errno);
 
-	btf = btf_get_from_fd(btf_fd, NULL);
+	btf = btf_get_from_fd(btf_fd, base_btf);
 	close(btf_fd);
 
 	return libbpf_ptr(btf);
 }
 
+struct btf *btf__load_from_kernel_by_id(__u32 id)
+{
+	return btf__load_from_kernel_by_id_split(id, NULL);
+}
+
 int btf__get_from_id(__u32 id, struct btf **btf)
 {
 	struct btf *res;

tools/lib/bpf/btf.h

@@ -45,6 +45,7 @@ LIBBPF_API struct btf *btf__parse_raw(const char *path);
 LIBBPF_API struct btf *btf__parse_raw_split(const char *path, struct btf *base_btf);
 
 LIBBPF_API struct btf *btf__load_from_kernel_by_id(__u32 id);
+LIBBPF_API struct btf *btf__load_from_kernel_by_id_split(__u32 id, struct btf *base_btf);
 LIBBPF_API int btf__get_from_id(__u32 id, struct btf **btf);
 
 LIBBPF_API int btf__finalize_data(struct bpf_object *obj, struct btf *btf);

tools/lib/bpf/libbpf.map

@@ -374,6 +374,7 @@ LIBBPF_0.5.0 {
 		bpf_map_lookup_and_delete_elem_flags;
 		bpf_object__gen_loader;
 		btf__load_from_kernel_by_id;
+		btf__load_from_kernel_by_id_split;
 		btf__load_into_kernel;
 		btf_dump__dump_type_data;
 		libbpf_set_strict_mode;