mainline inclusion
from mainline-5.11-rc1
commit 0cfdcd63
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=0cfdcd6378071f383c900e3d8862347e2af1d1ca

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

Add ability to get base BTF. It can be also used to check if BTF is split BTF.
Signed-off-by: NAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201202065244.530571-3-andrii@kernel.org
(cherry picked from commit 0cfdcd63)
Signed-off-by: NWang Yufen <wangyufen@huawei.com>