linux-kernel - Re: [PATCH bpf v1 2/3] selftests/bpf: Print a message when tester could not run a program

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Date:   Thu, 16 May 2019 08:50:35 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Krzesimir Nowak <krzesimir@...volk.io>
Cc:     bpf@...r.kernel.org,
        Iago López Galeiras <iago@...volk.io>,
        "Alban Crequy (Kinvolk)" <alban@...volk.io>,
        Shuah Khan <shuah@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrey Ignatov <rdna@...com>, linux-kselftest@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf v1 2/3] selftests/bpf: Print a message when tester
 could not run a program

On Thu, 16 May 2019 11:29:39 +0200, Krzesimir Nowak wrote:
> > > diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
> > > index ccd896b98cac..bf0da03f593b 100644
> > > --- a/tools/testing/selftests/bpf/test_verifier.c
> > > +++ b/tools/testing/selftests/bpf/test_verifier.c
> > > @@ -825,11 +825,20 @@ static int do_prog_test_run(int fd_prog, bool unpriv, uint32_t expected_val,
> > >                               tmp, &size_tmp, &retval, NULL);
> > >       if (unpriv)
> > >               set_admin(false);
> > > -     if (err && errno != 524/*ENOTSUPP*/ && errno != EPERM) {
> > > -             printf("Unexpected bpf_prog_test_run error ");
> > > -             return err;
> > > +     if (err) {
> > > +             switch (errno) {
> > > +             case 524/*ENOTSUPP*/:
> > > +                     printf("Did not run the program (not supported) ");
> > > +                     return 0;
> > > +             case EPERM:
> > > +                     printf("Did not run the program (no permission) ");
> > > +                     return 0;  
> >
> > Perhaps use strerror(errno)?  
> 
> As I said in the commit message, I open-coded those messages because
> strerror for ENOTSUPP returns "Unknown error 524".

Ah, sorry, missed that.  I wonder if that's something worth addressing
in libc, since the BPF subsystem uses ENOTSUPP a lot.