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libbpf: Add LIBBPF_DEPRECATED_SINCE macro for scheduling API deprecations

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Introduce a macro LIBBPF_DEPRECATED_SINCE(major, minor, message) to prepare
the deprecation of two API functions. This macro marks functions as deprecated
when libbpf's version reaches the values passed as an argument.

As part of this change libbpf_version.h header is added with recorded major
(LIBBPF_MAJOR_VERSION) and minor (LIBBPF_MINOR_VERSION) libbpf version macros.
They are now part of libbpf public API and can be relied upon by user code.
libbpf_version.h is installed system-wide along other libbpf public headers.

Due to this new build-time auto-generated header, in-kernel applications
relying on libbpf (resolve_btfids, bpftool, bpf_preload) are updated to
include libbpf's output directory as part of a list of include search paths.
Better fix would be to use libbpf's make_install target to install public API
headers, but that clean up is left out as a future improvement. The build
changes were tested by building kernel (with KBUILD_OUTPUT and O= specified
explicitly), bpftool, libbpf, selftests/bpf, and resolve_btfids builds. No
problems were detected.

Note that because of the constraints of the C preprocessor we have to write
a few lines of macro magic for each version used to prepare deprecation (0.6
for now).

Also, use LIBBPF_DEPRECATED_SINCE() to schedule deprecation of
btf__get_from_id() and btf__load(), which are replaced by
btf__load_from_kernel_by_id() and btf__load_into_kernel(), respectively,
starting from future libbpf v0.6. This is part of libbpf 1.0 effort ([0]).

  [0] Closes: https://github.com/libbpf/libbpf/issues/278

Co-developed-by: Quentin Monnet <quentin@isovalent.com>
Co-developed-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210908213226.1871016-1-andrii@kernel.org
This commit is contained in:
Quentin Monnet
2021-09-08 14:32:26 -07:00
committed by Andrii Nakryiko
parent 514bb47ac5
commit f8983f7fb0
2 changed files with 21 additions and 0 deletions
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src/btf.h
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@@ -50,9 +50,11 @@ LIBBPF_API struct btf *libbpf_find_kernel_btf(void);
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_DEPRECATED_SINCE(0, 6, "use btf__load_from_kernel_by_id instead")
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);
LIBBPF_DEPRECATED_SINCE(0, 6, "use btf__load_into_kernel instead")
LIBBPF_API int btf__load(struct btf *btf);
LIBBPF_API int btf__load_into_kernel(struct btf *btf);
LIBBPF_API __s32 btf__find_by_name(const struct btf *btf,