linux-kernel - Re: [External] Re: [PATCH bpf-next v2 8/9] libbpf: add support for the multi-link of tracing

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Date: Tue, 12 Mar 2024 10:44:06 +0800
From: 梦龙董 <dongmenglong.8@...edance.com>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Andrii Nakryiko <andrii@...nel.org>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Martin KaFai Lau <martin.lau@...ux.dev>, Eddy Z <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@...gle.com>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	Alexander Gordeev <agordeev@...ux.ibm.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>, 
	Sven Schnelle <svens@...ux.ibm.com>, "David S. Miller" <davem@...emloft.net>, 
	David Ahern <dsahern@...nel.org>, Dave Hansen <dave.hansen@...ux.intel.com>, 
	X86 ML <x86@...nel.org>, Steven Rostedt <rostedt@...dmis.org>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Quentin Monnet <quentin@...valent.com>, 
	bpf <bpf@...r.kernel.org>, 
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>, LKML <linux-kernel@...r.kernel.org>, 
	linux-riscv <linux-riscv@...ts.infradead.org>, linux-s390 <linux-s390@...r.kernel.org>, 
	Network Development <netdev@...r.kernel.org>, linux-trace-kernel@...r.kernel.org, 
	"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>, linux-stm32@...md-mailman.stormreply.com
Subject: Re: [External] Re: [PATCH bpf-next v2 8/9] libbpf: add support for
 the multi-link of tracing

On Tue, Mar 12, 2024 at 9:56 AM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Mon, Mar 11, 2024 at 2:35 AM Menglong Dong
> <dongmenglong.8@...edance.com> wrote:
> >
> >
> > -               err = libbpf_find_attach_btf_id(prog, attach_name, &btf_obj_fd, &btf_type_id);
> > +               name_end = strchr(attach_name, ',');
> > +               /* for multi-link tracing, use the first target symbol during
> > +                * loading.
> > +                */
> > +               if ((def & SEC_ATTACH_BTF_MULTI) && name_end) {
> > +                       int len = name_end - attach_name + 1;
> > +                       char *first_tgt;
> > +
> > +                       first_tgt = malloc(len);
> > +                       if (!first_tgt)
> > +                               return -ENOMEM;
> > +                       strncpy(first_tgt, attach_name, len);
> > +                       first_tgt[len - 1] = '\0';
> > +                       err = libbpf_find_attach_btf_id(prog, first_tgt, &btf_obj_fd,
> > +                                                       &btf_type_id);
> > +                       free(first_tgt);
> > +               } else {
> > +                       err = libbpf_find_attach_btf_id(prog, attach_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?

Thanks!
Menglong Dong