netdev - Re: [PATCH bpf-next v2 1/9] bpf: selftests: Use libbpf 1.0 API mode in bpf constructor

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Date:   Mon, 4 Apr 2022 14:44:23 +0800
From:   Yafang Shao <laoar.shao@...il.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, Martin Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        john fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v2 1/9] bpf: selftests: Use libbpf 1.0 API mode
 in bpf constructor

On Mon, Apr 4, 2022 at 9:24 AM Andrii Nakryiko
<andrii.nakryiko@...il.com> wrote:
>
> On Sun, Apr 3, 2022 at 7:43 AM Yafang Shao <laoar.shao@...il.com> wrote:
> >
> > In libbpf 1.0 API mode, it will bump rlimit automatically if there's no
> > memcg-basaed accounting, so we can use libbpf 1.0 API mode instead in case
> > we want to run it in an old kernel.
> >
> > The constructor is renamed to bpf_strict_all_ctor().
> >
> > Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> > ---
> >  tools/testing/selftests/bpf/bpf_rlimit.h | 26 +++---------------------
> >  1 file changed, 3 insertions(+), 23 deletions(-)
> >
> > diff --git a/tools/testing/selftests/bpf/bpf_rlimit.h b/tools/testing/selftests/bpf/bpf_rlimit.h
> > index 9dac9b30f8ef..d050f7d0bb5c 100644
> > --- a/tools/testing/selftests/bpf/bpf_rlimit.h
> > +++ b/tools/testing/selftests/bpf/bpf_rlimit.h
> > @@ -1,28 +1,8 @@
> >  #include <sys/resource.h>
> >  #include <stdio.h>
> >
> > -static  __attribute__((constructor)) void bpf_rlimit_ctor(void)
> > +static  __attribute__((constructor)) void bpf_strict_all_ctor(void)
>
> well, no, let's get rid of bpf_rlimit.h altogether. There is no need
> for constructor magic when you can have an explicit
> libbpf_set_strict_mode(LIBBPF_STRICT_ALL).
>

Sure, I will do it.

> >  {
> > -       struct rlimit rlim_old, rlim_new = {
> > -               .rlim_cur       = RLIM_INFINITY,
> > -               .rlim_max       = RLIM_INFINITY,
> > -       };
> > -
> > -       getrlimit(RLIMIT_MEMLOCK, &rlim_old);
> > -       /* For the sake of running the test cases, we temporarily
> > -        * set rlimit to infinity in order for kernel to focus on
> > -        * errors from actual test cases and not getting noise
> > -        * from hitting memlock limits. The limit is on per-process
> > -        * basis and not a global one, hence destructor not really
> > -        * needed here.
> > -        */
> > -       if (setrlimit(RLIMIT_MEMLOCK, &rlim_new) < 0) {
> > -               perror("Unable to lift memlock rlimit");
> > -               /* Trying out lower limit, but expect potential test
> > -                * case failures from this!
> > -                */
> > -               rlim_new.rlim_cur = rlim_old.rlim_cur + (1UL << 20);
> > -               rlim_new.rlim_max = rlim_old.rlim_max + (1UL << 20);
> > -               setrlimit(RLIMIT_MEMLOCK, &rlim_new);
> > -       }
> > +       /* Use libbpf 1.0 API mode */
> > +       libbpf_set_strict_mode(LIBBPF_STRICT_ALL);
> >  }
> > --
> > 2.17.1
> >

-- 
Thanks
Yafang