linux-kernel - Re: [PATCH v2 bpf-next] libbpf: Add bpf_obj_get

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Date:   Fri, 29 Jul 2022 20:20:05 +0000
From:   Joe Burton <jevburton@...gle.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Joe Burton <jevburton.kernel@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 bpf-next] libbpf: Add bpf_obj_get_opts()

On Wed, Jul 27, 2022 at 04:02:43PM -0700, Andrii Nakryiko wrote:

Applied both of these in v3, which I'll send out in a moment. Thanks for
the feedback!

> >  int bpf_obj_get(const char *pathname)
> > +{
> > +       LIBBPF_OPTS(bpf_obj_get_opts, opts);
> 
> if you were doing it this way, here should be an empty line. But
> really you can/should just pass NULL instead of opts in this case.

> > +struct bpf_obj_get_opts {
> > +       size_t sz; /* size of this struct for forward/backward compatibility */
> > +
> > +       __u32 file_flags;
> 
> please add size_t :0; to avoid non-zero-initialized padding  (we do it
> in a lot of other opts structs)
> 

TIL about this trick. Very clever.