Re: [PATCH dwarves v3 0/2] btf: support BTF_KIND_ENUM64

From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Yonghong Song <yhs@fb.com>
Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
	dwarves@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
	Andrii Nakryiko <andrii@kernel.org>,
	bpf@vger.kernel.org, Daniel Borkmann <daniel@iogearbox.net>,
	kernel-team@fb.com
Subject: Re: [PATCH dwarves v3 0/2] btf: support BTF_KIND_ENUM64
Date: Wed, 29 Jun 2022 18:44:52 -0300	[thread overview]
Message-ID: <YrzH1ABPYmKSEogS@kernel.org> (raw)
In-Reply-To: <20220629071213.3178592-1-yhs@fb.com>

Em Wed, Jun 29, 2022 at 12:12:13AM -0700, Yonghong Song escreveu:
> Add support for enum64. For 64-bit enumerator value,
> previously, the value is truncated into 32bit, e.g.,
> for the following enum in linux uapi bpf.h,
>   enum {
>         BPF_F_INDEX_MASK                = 0xffffffffULL,
>         BPF_F_CURRENT_CPU               = BPF_F_INDEX_MASK,
>   /* BPF_FUNC_perf_event_output for sk_buff input context. */
>         BPF_F_CTXLEN_MASK               = (0xfffffULL << 32),
>   };    

Applied, added the entry for skip generating enums to the man page,
added support to the pahole BTF loader, used the new pahole to build
bpf-next/master, all seems ok, pushing to next on git.kernel.org so that
the libbpf github CI can give it a go.

To build with torvalds/master one has to add --skip_encoding_btf_enum64,
I think, haven't tested with it, without it isn't working, libbpf
complains at that btfids tool.

Please check/test what is in there now:

  git://git.kernel.org/pub/scm/devel/pahole/pahole.git next
  https://git.kernel.org/pub/scm/devel/pahole/pahole.git/log/?h=next

Unless someone screams I plan pushing out a new release, update fedora
packages, etc early next week its overdue by now.

- Arnaldo

> BPF_F_CTXLEN_MASK will be encoded with 0 with BTF_KIND_ENUM
> after pahole dwarf-to-btf conversion.
> With this patch, the BPF_F_CTXLEN_MASK will be encoded properly
> with BTF_KIND_ENUM64.
> 
> This patch is on top of tmp.master since tmp.master has not
> been sync'ed with master branch yet.
> 
> Changelogs:
>   v2 -> v3:
>     - pass struct type/conf_load pointers to btf_encoder__add_enum[_value]
>       to make code easier to understand.
>   v1 -> v2:
>     - Add flag --skip_encoding_btf_enum64 to disable newly-added functionality.
> 
> Yonghong Song (2):
>   libbpf: Sync with latest libbpf repo
>   btf: Support BTF_KIND_ENUM64
> 
>  btf_encoder.c     | 67 +++++++++++++++++++++++++++++++++++------------
>  btf_encoder.h     |  2 +-
>  dwarf_loader.c    | 12 +++++++++
>  dwarves.h         |  4 ++-
>  dwarves_fprintf.c |  6 ++++-
>  lib/bpf           |  2 +-
>  pahole.c          | 10 ++++++-
>  7 files changed, 81 insertions(+), 22 deletions(-)
> 
> -- 
> 2.30.2

-- 

- Arnaldo