[PATCH bpf-next] libbpf: deprecate btf_ext rec_size APIs

[PATCH bpf-next] libbpf: deprecate btf_ext rec_size APIs

[Dave Marchevsky]

btf_ext__{func,line}_info_rec_size functions are used in conjunction
with already-deprecated btf_ext__reloc_{func,line}_info functions. Since
struct btf_ext is opaque to the user it was necessary to expose rec_size
getters in the past.

btf_ext__reloc_{func,line}_info were deprecated in commit 8505e8709b5ee
("libbpf: Implement generalized .BTF.ext func/line info adjustment")
as they're not compatible with support for multiple programs per
section. It was decided[0] that users of these APIs should implement their
own .btf.ext parsing to access this data, in which case the rec_size
getters are unnecessary. So deprecate them from libbpf 0.7.0 onwards.

  [0] Closes: https://github.com/libbpf/libbpf/issues/277

Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
---
 tools/lib/bpf/btf.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 96b44d55db6e..c2f89a2cca11 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -168,7 +168,9 @@ int btf_ext__reloc_line_info(const struct btf *btf,
 			     const struct btf_ext *btf_ext,
 			     const char *sec_name, __u32 insns_cnt,
 			     void **line_info, __u32 *cnt);
+LIBBPF_DEPRECATED_SINCE(0, 7, "btf_ext__reloc_func_info is deprecated; write custom func_info parsing to fetch rec_size")
 LIBBPF_API __u32 btf_ext__func_info_rec_size(const struct btf_ext *btf_ext);
+LIBBPF_DEPRECATED_SINCE(0, 7, "btf_ext__reloc_line_info is deprecated; write custom line_info parsing to fetch rec_size")
 LIBBPF_API __u32 btf_ext__line_info_rec_size(const struct btf_ext *btf_ext);
 
 LIBBPF_API int btf__find_str(struct btf *btf, const char *s);
-- 
2.30.2

Re: [PATCH bpf-next] libbpf: deprecate btf_ext rec_size APIs

[Daniel Borkmann]

On 1/27/22 7:21 PM, Dave Marchevsky wrote:
> btf_ext__{func,line}_info_rec_size functions are used in conjunction
> with already-deprecated btf_ext__reloc_{func,line}_info functions. Since
> struct btf_ext is opaque to the user it was necessary to expose rec_size
> getters in the past.
> 
> btf_ext__reloc_{func,line}_info were deprecated in commit 8505e8709b5ee
> ("libbpf: Implement generalized .BTF.ext func/line info adjustment")
> as they're not compatible with support for multiple programs per
> section. It was decided[0] that users of these APIs should implement their
> own .btf.ext parsing to access this data, in which case the rec_size
> getters are unnecessary. So deprecate them from libbpf 0.7.0 onwards.
> 
>    [0] Closes: https://github.com/libbpf/libbpf/issues/277
> 
> Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com>
> ---
>   tools/lib/bpf/btf.h | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
> index 96b44d55db6e..c2f89a2cca11 100644
> --- a/tools/lib/bpf/btf.h
> +++ b/tools/lib/bpf/btf.h
> @@ -168,7 +168,9 @@ int btf_ext__reloc_line_info(const struct btf *btf,
>   			     const struct btf_ext *btf_ext,
>   			     const char *sec_name, __u32 insns_cnt,
>   			     void **line_info, __u32 *cnt);
> +LIBBPF_DEPRECATED_SINCE(0, 7, "btf_ext__reloc_func_info is deprecated; write custom func_info parsing to fetch rec_size")
>   LIBBPF_API __u32 btf_ext__func_info_rec_size(const struct btf_ext *btf_ext);
> +LIBBPF_DEPRECATED_SINCE(0, 7, "btf_ext__reloc_line_info is deprecated; write custom line_info parsing to fetch rec_size")
>   LIBBPF_API __u32 btf_ext__line_info_rec_size(const struct btf_ext *btf_ext);

The btf_ext__reloc_{func,line}_info() only use LIBBPF_DEPRECATED() instead of
LIBBPF_DEPRECATED_SINCE(). If they are used in conjunction with the other ones,
should we either mark all of them LIBBPF_DEPRECATED_SINCE(0, 7, [...]) or just
all as LIBBPF_DEPRECATED() ?

>   LIBBPF_API int btf__find_str(struct btf *btf, const char *s);
> 

Thanks,
Daniel