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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date: Tue, 12 Mar 2024 09:11:41 -0700
Message-ID: <CAADnVQJ87Ov6ny2hj-0_WymGB3TeuEZu373EmqmRJqZv-8Ze_Q@mail.gmail.com>
Subject: Re: [External] Re: [PATCH bpf-next v2 8/9] libbpf: add support for
 the multi-link of tracing
To: =?UTF-8?B?5qKm6b6Z6JGj?= <dongmenglong.8@bytedance.com>
Cc: Andrii Nakryiko <andrii@kernel.org>, Alexei Starovoitov <ast@kernel.org>, 
	Daniel Borkmann <daniel@iogearbox.net>, Martin KaFai Lau <martin.lau@linux.dev>, Eddy Z <eddyz87@gmail.com>, 
	Song Liu <song@kernel.org>, Yonghong Song <yonghong.song@linux.dev>, 
	John Fastabend <john.fastabend@gmail.com>, KP Singh <kpsingh@kernel.org>, 
	Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>, 
	Alexander Gordeev <agordeev@linux.ibm.com>, Christian Borntraeger <borntraeger@linux.ibm.com>, 
	Sven Schnelle <svens@linux.ibm.com>, "David S. Miller" <davem@davemloft.net>, 
	David Ahern <dsahern@kernel.org>, Dave Hansen <dave.hansen@linux.intel.com>, 
	X86 ML <x86@kernel.org>, Steven Rostedt <rostedt@goodmis.org>, 
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>, Quentin Monnet <quentin@isovalent.com>, 
	bpf <bpf@vger.kernel.org>, 
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>, LKML <linux-kernel@vger.kernel.org>, 
	linux-riscv <linux-riscv@lists.infradead.org>, linux-s390 <linux-s390@vger.kernel.org>, 
	Network Development <netdev@vger.kernel.org>, linux-trace-kernel@vger.kernel.org, 
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@vger.kernel.org>, linux-stm32@st-md-mailman.stormreply.com
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On Mon, Mar 11, 2024 at 7:44=E2=80=AFPM =E6=A2=A6=E9=BE=99=E8=91=A3 <dongme=
nglong.8@bytedance.com> wrote:
>
> On Tue, Mar 12, 2024 at 9:56=E2=80=AFAM Alexei Starovoitov
> <alexei.starovoitov@gmail.com> wrote:
> >
> > On Mon, Mar 11, 2024 at 2:35=E2=80=AFAM Menglong Dong
> > <dongmenglong.8@bytedance.com> wrote:
> > >
> > >
> > > -               err =3D libbpf_find_attach_btf_id(prog, attach_name, =
&btf_obj_fd, &btf_type_id);
> > > +               name_end =3D strchr(attach_name, ',');
> > > +               /* for multi-link tracing, use the first target symbo=
l during
> > > +                * loading.
> > > +                */
> > > +               if ((def & SEC_ATTACH_BTF_MULTI) && name_end) {
> > > +                       int len =3D name_end - attach_name + 1;
> > > +                       char *first_tgt;
> > > +
> > > +                       first_tgt =3D malloc(len);
> > > +                       if (!first_tgt)
> > > +                               return -ENOMEM;
> > > +                       strncpy(first_tgt, attach_name, len);
> > > +                       first_tgt[len - 1] =3D '\0';
> > > +                       err =3D libbpf_find_attach_btf_id(prog, first=
_tgt, &btf_obj_fd,
> > > +                                                       &btf_type_id)=
;
> > > +                       free(first_tgt);
> > > +               } else {
> > > +                       err =3D libbpf_find_attach_btf_id(prog, attac=
h_name, &btf_obj_fd,
> > > +                                                       &btf_type_id)=
;
> > > +               }
> >
> > Pls use glob_match the way [ku]probe multi are doing
> > instead of exact match.
>
> Hello,
>
> I'm a little suspecting the effect of glob_match. I seldom found
> the use case that the kernel functions which we want to trace
> have the same naming pattern. And the exact match seems more
> useful.
>
> Can we use both exact and glob match here?

exact is a subset of glob_match.
Pls follow the pattern that[ku]probe multi established
in terms of user interface expectations.