Re: [PATCH -next v2] bpf/benchs: Fix return value check of bpf_program__attach()

From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Yonghong Song <yhs@fb.com>
Cc: Yang Yingliang <yangyingliang@huawei.com>,
	Joanne Koong <joannekoong@fb.com>,
	Andrii Nakryiko <andrii@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	"open list:KERNEL SELFTEST FRAMEWORK" 
	<linux-kselftest@vger.kernel.org>, Shuah Khan <shuah@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>
Subject: Re: [PATCH -next v2] bpf/benchs: Fix return value check of bpf_program__attach()
Date: Mon, 1 Nov 2021 15:30:31 -0700	[thread overview]
Message-ID: <CAADnVQ+aeAnBEN=dp92q0RBXT+Um1ha4_F=sQ7fr08Sa3qauLQ@mail.gmail.com> (raw)
In-Reply-To: <90518c5d-36ea-ec97-9f14-0687fdd6074f@fb.com>

On Mon, Nov 1, 2021 at 3:21 PM Yonghong Song <yhs@fb.com> wrote:
>
>
>
> On 11/1/21 3:00 PM, Alexei Starovoitov wrote:
> > On Mon, Nov 1, 2021 at 5:35 AM Yang Yingliang <yangyingliang@huawei.com> wrote:
> >>
> >> If bpf_program__attach() fails, it never returns NULL,
> >> we should use libbpf_get_error() to check the return value.
> >>
> >> Reported-by: Hulk Robot <hulkci@huawei.com>
> >> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
> >> Acked-by: Yonghong Song <yhs@fb.com>
> >> ---
> >> v2:
> >>    don't use 'int err'
> >> ---
> >>   .../selftests/bpf/benchs/bench_bloom_filter_map.c      | 10 +++++-----
> >>   1 file changed, 5 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/tools/testing/selftests/bpf/benchs/bench_bloom_filter_map.c b/tools/testing/selftests/bpf/benchs/bench_bloom_filter_map.c
> >> index 6eeeed2913e6..4afaa4adb327 100644
> >> --- a/tools/testing/selftests/bpf/benchs/bench_bloom_filter_map.c
> >> +++ b/tools/testing/selftests/bpf/benchs/bench_bloom_filter_map.c
> >> @@ -304,7 +304,7 @@ static void bloom_lookup_setup(void)
> >>          populate_maps();
> >>
> >>          link = bpf_program__attach(ctx.skel->progs.bloom_lookup);
> >> -       if (!link) {
> >> +       if (libbpf_get_error(link)) {
> >
> > Please use ASSERT_OK_PTR() instead.
> > See how other tests are doing it.
>
> I actually looked at this. ASSERT_OK_PTR() is defined in test_progs.h
> and test_progs.h is ONLY included in files which eventually linked to
> test_progs. That is why I didn't recommend to use ASSERT_OK_PTR().
>
> Maybe it is okay to include test_progs.h in benchs/*.c. Or we may
> want to refactor to a separate header file to contain these macros
> which can be used for test_progs.h and other applications.

hmm.
Looks like bench_ringbufs.c has the same issue doing:
if (!link)
and bench_rename.c too.

Probably would be good to fix in all bench-s.

If test_progs.h cannot be included directly
copy-pasting ASSERT_OK_PTR in a reduced form into bench.h
is probably cleaner than open coding libbpf_get_error.