From: Eduard Zingerman <eddyz87@gmail.com>
To: "Toke Høiland-Jørgensen" <toke@kernel.org>,
"Alexei Starovoitov" <alexei.starovoitov@gmail.com>,
"Andrii Nakryiko" <andrii.nakryiko@gmail.com>
Cc: Alan Maguire <alan.maguire@oracle.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>,
Quentin Monnet <quentin@isovalent.com>,
Mykola Lysenko <mykolal@fb.com>, bpf <bpf@vger.kernel.org>
Subject: Re: [RFC bpf-next 1/8] btf: add kind metadata encoding to UAPI
Date: Wed, 07 Jun 2023 14:55:42 +0300 [thread overview]
Message-ID: <35e5f70bbe0890f875e0c24aff0453c25f018ea6.camel@gmail.com> (raw)
In-Reply-To: <878rcw3k1o.fsf@toke.dk>
On Tue, 2023-06-06 at 13:30 +0200, Toke Høiland-Jørgensen wrote:
[...]
>
> As for bumping the version number, I don't think it's a good idea to
> deliberately break compatibility this way unless it's absolutely
> necessary. With "absolutely necessary" meaning "things will break in
> subtle ways in any case, so it's better to make the breakage obvious".
> But it libbpf is not checking the version field anyway, that becomes
> kind of a moot point, as bumping it doesn't really gain us anything,
> then...
It seems to me that in terms of backward compatibility, the ability to
specify the size for each kind entry is more valuable than the
capability to add new BTF kinds:
- The former allows for extending kind records in
a backward-compatible manner, such as adding a function address to
BTF_KIND_FUNC.
- The latter is much more fragile. Types refer to each other,
compatibility is already lost once a new "unknown" tag is introduced
in a type chain.
However, changing the size of existing BTF kinds is itself a
backward-incompatible change. Therefore, a version bump may be
warranted in this regard.
next prev parent reply other threads:[~2023-06-07 11:55 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-31 20:19 [RFC bpf-next 0/8] bpf: support BTF kind metadata to separate Alan Maguire
2023-05-31 20:19 ` [RFC bpf-next 1/8] btf: add kind metadata encoding to UAPI Alan Maguire
2023-06-01 3:53 ` Alexei Starovoitov
2023-06-01 10:36 ` Alan Maguire
2023-06-01 16:53 ` Alexei Starovoitov
2023-06-02 16:32 ` Andrii Nakryiko
2023-06-02 16:34 ` Andrii Nakryiko
2023-06-02 18:11 ` Alexei Starovoitov
2023-06-02 20:33 ` Andrii Nakryiko
2023-06-05 16:14 ` Alexei Starovoitov
2023-06-05 22:38 ` Andrii Nakryiko
2023-06-06 2:46 ` Alexei Starovoitov
2023-06-06 11:30 ` Toke Høiland-Jørgensen
2023-06-07 11:55 ` Eduard Zingerman [this message]
2023-06-07 15:29 ` Yonghong Song
2023-06-07 16:14 ` Eduard Zingerman
2023-06-07 21:47 ` Andrii Nakryiko
2023-06-07 22:05 ` Eduard Zingerman
2023-06-07 22:34 ` Andrii Nakryiko
2023-06-06 16:50 ` Andrii Nakryiko
2023-06-07 1:16 ` Alexei Starovoitov
2023-06-07 21:43 ` Andrii Nakryiko
2023-05-31 20:19 ` [RFC bpf-next 2/8] libbpf: support handling of metadata section in BTF Alan Maguire
2023-06-05 11:01 ` Jiri Olsa
2023-06-05 21:40 ` Andrii Nakryiko
2023-05-31 20:19 ` [RFC bpf-next 3/8] libbpf: use metadata to compute an unknown kind size Alan Maguire
2023-05-31 20:19 ` [RFC bpf-next 4/8] btf: support kernel parsing of BTF with metadata, use it to parse BTF with unknown kinds Alan Maguire
2023-06-07 19:51 ` Eduard Zingerman
2023-05-31 20:19 ` [RFC bpf-next 5/8] libbpf: add metadata encoding support Alan Maguire
2023-05-31 20:19 ` [RFC bpf-next 6/8] btf: generate metadata for vmlinux/module BTF Alan Maguire
2023-05-31 20:19 ` [RFC bpf-next 7/8] bpftool: add BTF dump "format meta" to dump header/metadata Alan Maguire
2023-06-01 16:33 ` Quentin Monnet
2023-06-02 16:57 ` Andrii Nakryiko
2023-05-31 20:19 ` [RFC bpf-next 8/8] selftests/bpf: test kind encoding/decoding Alan Maguire
2023-05-31 20:19 ` [RFC dwarves] dwarves: encode BTF metadata if --btf_gen_meta is set Alan Maguire
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