linux-kernel - Re: [RFC PATCH v4 1/7] libbpf: Extract BTF type remapping logic into helper function

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Message-ID: <ba6272aa416c80c8a4800945b6ed311fe1506a74.camel@gmail.com>
Date: Tue, 04 Nov 2025 15:16:30 -0800
From: Eduard Zingerman <eddyz87@...il.com>
To: Donglin Peng <dolinux.peng@...il.com>, ast@...nel.org
Cc: linux-kernel@...r.kernel.org, bpf@...r.kernel.org, Andrii Nakryiko	
 <andrii.nakryiko@...il.com>, Alan Maguire <alan.maguire@...cle.com>, Song
 Liu	 <song@...nel.org>, pengdonglin <pengdonglin@...omi.com>
Subject: Re: [RFC PATCH v4 1/7] libbpf: Extract BTF type remapping logic
 into helper function

On Tue, 2025-11-04 at 21:40 +0800, Donglin Peng wrote:
> From: pengdonglin <pengdonglin@...omi.com>
> 
> Refactor btf_dedup_remap_types() by extracting its core logic into a new
> btf_remap_types() helper function. This eliminates code duplication
> and improves modularity while maintaining the same functionality.
> 
> The new function encapsulates iteration over BTF types and BTF ext
> sections, accepting a callback for flexible type ID remapping. This
> makes the type remapping logic more maintainable and reusable.
> 
> Cc: Eduard Zingerman <eddyz87@...il.com>
> Cc: Alexei Starovoitov <ast@...nel.org>
> Cc: Andrii Nakryiko <andrii.nakryiko@...il.com>
> Cc: Alan Maguire <alan.maguire@...cle.com>
> Cc: Song Liu <song@...nel.org>
> Signed-off-by: pengdonglin <pengdonglin@...omi.com>
> Signed-off-by: Donglin Peng <dolinux.peng@...il.com>
> ---

Reviewed-by: Eduard Zingerman <eddyz87@...il.com>

>  tools/lib/bpf/btf.c             | 63 +++++++++++++++++----------------
>  tools/lib/bpf/libbpf_internal.h |  1 +
>  2 files changed, 33 insertions(+), 31 deletions(-)
> 
> diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
> index 18907f0fcf9f..5e1c09b5dce8 100644
> --- a/tools/lib/bpf/btf.c
> +++ b/tools/lib/bpf/btf.c
> @@ -3400,6 +3400,37 @@ int btf_ext__set_endianness(struct btf_ext *btf_ext, enum btf_endianness endian)
>  	return 0;
>  }
>  
> +static int btf_remap_types(struct btf *btf, struct btf_ext *btf_ext,
> +			   btf_remap_type_fn visit, void *ctx)
                           ^^^^^^^^^^^^^^^^^
Nit: there is already 'type_id_visit_fn', no need to add new type.

> +{
> +	int i, r;
> +
> +	for (i = 0; i < btf->nr_types; i++) {
> +		struct btf_type *t = btf_type_by_id(btf, btf->start_id + i);
> +		struct btf_field_iter it;
> +		__u32 *type_id;
> +
> +		r = btf_field_iter_init(&it, t, BTF_FIELD_ITER_IDS);
> +		if (r)
> +			return r;
> +
> +		while ((type_id = btf_field_iter_next(&it))) {
> +			r = visit(type_id, ctx);
> +			if (r)
> +				return r;
> +		}
> +	}
> +
> +	if (!btf_ext)
> +		return 0;
> +
> +	r = btf_ext_visit_type_ids(btf_ext, visit, ctx);
> +	if (r)
> +		return r;
> +
> +	return 0;
> +}
> +
>  struct btf_dedup;
>  
>  static struct btf_dedup *btf_dedup_new(struct btf *btf, const struct btf_dedup_opts *opts);

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