Re: [PATCH bpf-next] tools: libbpf: update extended attributes version of bpf_object__open()

From: Anton Protopopov <a.s.protopopov@gmail.com>
To: Song Liu <songliubraving@fb.com>
Cc: Andrii Nakryiko <andriin@fb.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>, Martin Lau <kafai@fb.com>,
	Yonghong Song <yhs@fb.com>, Networking <netdev@vger.kernel.org>,
	bpf <bpf@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH bpf-next] tools: libbpf: update extended attributes version of bpf_object__open()
Date: Fri, 30 Aug 2019 14:53:14 -0400	[thread overview]
Message-ID: <CAGn_itwS=bLf8NGVNbByNx8FmR_JtPWnuEnKO23ig8xnK_GYOw@mail.gmail.com> (raw)
In-Reply-To: <796E4DA8-4844-4708-866E-A8AE9477E94E@fb.com>

чт, 29 авг. 2019 г. в 16:02, Song Liu <songliubraving@fb.com>:
>
>
>
> > On Aug 14, 2019, at 5:03 PM, Anton Protopopov <a.s.protopopov@gmail.com> wrote:
> >
>
> [...]
>
> >
> >
> > int bpf_object__unload(struct bpf_object *obj)
> > diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> > index e8f70977d137..634f278578dd 100644
> > --- a/tools/lib/bpf/libbpf.h
> > +++ b/tools/lib/bpf/libbpf.h
> > @@ -63,8 +63,13 @@ LIBBPF_API libbpf_print_fn_t libbpf_set_print(libbpf_print_fn_t fn);
> > struct bpf_object;
> >
> > struct bpf_object_open_attr {
> > -     const char *file;
> > +     union {
> > +             const char *file;
> > +             const char *obj_name;
> > +     };
> >       enum bpf_prog_type prog_type;
> > +     void *obj_buf;
> > +     size_t obj_buf_sz;
> > };
>
> I think this would break dynamically linked libbpf. No?

Ah, yes, sure. What is the right way to make changes which break ABI in libbpf?

BTW, does the commit ddc7c3042614 ("libbpf: implement BPF CO-RE offset
relocation algorithm") which adds a new field to the struct
bpf_object_load_attr also break ABI?

>
> Thanks,
> Song
>