libbpf: Add split BTF support for btf__load_from_kernel_by_id()

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

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 948c29f..cafa4f6 100644 (file)
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1383,7 +1383,7 @@ 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;
@@ -1392,12 +1392,17 @@ 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;

diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 5d95532..596a42c 100644 (file)
--- a/tools/lib/bpf/btf.h
+++ b/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);

diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 3a9c693..5aca368 100644 (file)
--- 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;