Re: [PATCH v3 bpf-next] bpftool: introduce btf c dump sorting

[Alexei Starovoitov <alexei.starovoitov@gmail.com>]

On Mon, May 13, 2024 at 4:08 PM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Mon, May 13, 2024 at 1:29 PM Mykyta Yatsenko
> <mykyta.yatsenko5@gmail.com> wrote:
> >
> > From: Mykyta Yatsenko <yatsenko@meta.com>
> >
> > Sort bpftool c dump output; aiming to simplify vmlinux.h diffing and
> > forcing more natural type definitions ordering.
> >
> > Definitions are sorted first by their BTF kind ranks, then by their base
> > type name and by their own name.
> >
> > Type ranks
> >
> > Assign ranks to btf kinds (defined in function btf_type_rank) to set
> > next order:
> > 1. Anonymous enums/enums64
> > 2. Named enums/enums64
> > 3. Trivial types typedefs (ints, then floats)
> > 4. Structs/Unions
> > 5. Function prototypes
> > 6. Forward declarations
> >
> > Type rank is set to maximum for unnamed reference types, structs and
> > unions to avoid emitting those types early. They will be emitted as
> > part of the type chain starting with named type.
> >
> > Lexicographical ordering
> >
> > Each type is assigned a sort_name and own_name.
> > sort_name is the resolved name of the final base type for reference
> > types (typedef, pointer, array etc). Sorting by sort_name allows to
> > group typedefs of the same base type. sort_name for non-reference type
> > is the same as own_name. own_name is a direct name of particular type,
> > is used as final sorting step.
> >
> > Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
> > ---
> >  .../bpf/bpftool/Documentation/bpftool-btf.rst |   5 +-
> >  tools/bpf/bpftool/bash-completion/bpftool     |   3 +
> >  tools/bpf/bpftool/btf.c                       | 138 +++++++++++++++++-
> >  3 files changed, 139 insertions(+), 7 deletions(-)
> >
>
> LGTM, tried it locally and it works well. In fact, see 6.8 kernel vs
> latest bpf-next/master (with basically the same config) comparison.
> It's quite minimal and easy to use to see what changes about some of
> the BPF internal types.
>
> Acked-by: Andrii Nakryiko <andrii@kernel.org>
> Tested-by: Andrii Nakryiko <andrii@kernel.org>
>
>   [0] https://gist.github.com/anakryiko/8fd8ebf2aba73961ebd3cf6587de6822

Just noticed:

+ ETHTOOL_A_TS_STAT_UNSPEC = 0,
+ ETHTOOL_A_TS_STAT_TX_PKTS = 1,
+ ETHTOOL_A_TS_STAT_TX_LOST = 2,
+ ETHTOOL_A_TS_STAT_TX_ERR = 3,
+ __ETHTOOL_A_TS_STAT_CNT = 4,
+ ETHTOOL_A_TS_STAT_MAX = 3,
};

I'm a bit surprised that enum values are not sorted.
I'm guessing the enum names come in dwarf order and copied
the same way in BTF ?
I guess it's not an issue.