From: Quentin Monnet <quentin@isovalent.com>
Date: Thu, 29 Jul 2021 17:20:27 +0100
Subject: libbpf: Add split BTF support for btf__load_from_kernel_by_id()
Patch-mainline: v5.15-rc1
Git-commit: 61fc51b1d3e5915e356f2c0b67cd3bb13b640413
References: jsc#PED-1377

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/314

Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210729162028.29512-8-quentin@isovalent.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 tools/lib/bpf/btf.c      |    9 +++++++--
 tools/lib/bpf/btf.h      |    1 +
 tools/lib/bpf/libbpf.map |    1 +
 3 files changed, 9 insertions(+), 2 deletions(-)

--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1382,7 +1382,7 @@ exit_free:
 	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;
@@ -1391,12 +1391,17 @@ struct btf *btf__load_from_kernel_by_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;
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -45,6 +45,7 @@ LIBBPF_API struct btf *btf__parse_raw(co
 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);
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -376,6 +376,7 @@ LIBBPF_0.5.0 {
 		bpf_program__attach_kprobe_opts;
 		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;