linux-kernel - Re: [PATCH] libbpf: optimize the redundant code in the bpf_object__init_user_btf

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Message-ID: <CAHP3+4Dg7aBqaVWs5vfydtWuSpuRS+p43XNJk9TwxAPrVm=7NQ@mail.gmail.com>
Date: Fri, 24 Oct 2025 15:55:51 +0800
From: Jianyun Gao <jianyungao89@...il.com>
To: Jiri Olsa <olsajiri@...il.com>
Cc: linux-kernel@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, 
	Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
	"open list:BPF [GENERAL] (Safe Dynamic Programs and Tools)" <bpf@...r.kernel.org>
Subject: Re: [PATCH] libbpf: optimize the redundant code in the
 bpf_object__init_user_btf_maps() function.

Hi Jiri, thank you for your review. And I have realized my mistake in
this patch. I will fix it in the next patch!

On Fri, Oct 24, 2025 at 2:57 PM Jiri Olsa <olsajiri@...il.com> wrote:
>
> On Fri, Oct 24, 2025 at 02:07:20PM +0800, Jianyun Gao wrote:
> > In the elf_sec_data() function, the input parameter 'scn' will be
> > evaluated. If it is NULL, then it will directly return NULL. Therefore,
> > the return value of the elf_sec_data() function already takes into
> > account the case where the input parameter scn is NULL. Therefore,
> > subsequently, the code only needs to check whether the return value of
> > the elf_sec_data() function is NULL.
> >
> > Signed-off-by: Jianyun Gao <jianyungao89@...il.com>
> > ---
> >  tools/lib/bpf/libbpf.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index b90574f39d1c..9e66104a61eb 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -2988,15 +2988,15 @@ static int bpf_object__init_user_btf_maps(struct bpf_object *obj, bool strict,
> >       int nr_types, i, vlen, err;
> >       const struct btf_type *t;
> >       const char *name;
> > -     Elf_Data *data;
> > +     Elf_Data *scn_data;
>
> makes sense to me, but this rename breaks compilation later on
>
> libbpf.c:3027:53: error: ‘data’ undeclared (first use in this function)
>
> jirka
>
> >       Elf_Scn *scn;
> >
> >       if (obj->efile.btf_maps_shndx < 0)
> >               return 0;
> >
> >       scn = elf_sec_by_idx(obj, obj->efile.btf_maps_shndx);
> > -     data = elf_sec_data(obj, scn);
> > -     if (!scn || !data) {
> > +     scn_data = elf_sec_data(obj, scn);
> > +     if (!scn_data) {
> >               pr_warn("elf: failed to get %s map definitions for %s\n",
> >                       MAPS_ELF_SEC, obj->path);
> >               return -EINVAL;
> > --
> > 2.34.1
> >