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([2620:10d:c090:500::6:8aee]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-ba902c9d0d4sm346296a12.36.2025.11.05.14.52.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Nov 2025 14:52:19 -0800 (PST) Message-ID: Subject: Re: [bpf-next] selftests/bpf: refactor snprintf_btf test to use bpf_strncmp From: Eduard Zingerman To: Alexei Starovoitov , Hoyeon Lee Cc: Alexei Starovoitov , Daniel Borkmann , bpf , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shuah Khan , "open list:KERNEL SELFTEST FRAMEWORK" , LKML Date: Wed, 05 Nov 2025 14:52:18 -0800 In-Reply-To: References: <20251105201415.227144-1-hoyeon.lee@suse.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-1.fc42) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2025-11-05 at 14:45 -0800, Alexei Starovoitov wrote: > On Wed, Nov 5, 2025 at 12:14=E2=80=AFPM Hoyeon Lee = wrote: > >=20 > > The netif_receive_skb BPF program used in snprintf_btf test still uses > > a custom __strncmp. This is unnecessary as the bpf_strncmp helper is > > available and provides the same functionality. > >=20 > > This commit refactors the test to use the bpf_strncmp helper, removing > > the redundant custom implementation. > >=20 > > Signed-off-by: Hoyeon Lee > > --- > > .../selftests/bpf/progs/netif_receive_skb.c | 15 +-------------- > > 1 file changed, 1 insertion(+), 14 deletions(-) > >=20 > > diff --git a/tools/testing/selftests/bpf/progs/netif_receive_skb.c b/to= ols/testing/selftests/bpf/progs/netif_receive_skb.c > > index 9e067dcbf607..186b8c82b9e6 100644 > > --- a/tools/testing/selftests/bpf/progs/netif_receive_skb.c > > +++ b/tools/testing/selftests/bpf/progs/netif_receive_skb.c > > @@ -31,19 +31,6 @@ struct { > > __type(value, char[STRSIZE]); > > } strdata SEC(".maps"); > >=20 > > -static int __strncmp(const void *m1, const void *m2, size_t len) > > -{ > > - const unsigned char *s1 =3D m1; > > - const unsigned char *s2 =3D m2; > > - int i, delta =3D 0; > > - > > - for (i =3D 0; i < len; i++) { > > - delta =3D s1[i] - s2[i]; > > - if (delta || s1[i] =3D=3D 0 || s2[i] =3D=3D 0) > > - break; > > - } > > - return delta; > > -} > >=20 > > #if __has_builtin(__builtin_btf_type_id) > > #define TEST_BTF(_str, _type, _flags, _expected, ...) = \ > > @@ -69,7 +56,7 @@ static int __strncmp(const void *m1, const void *m2, = size_t len) > > &_ptr, sizeof(_ptr), _hflags); = \ > > if (ret) = \ > > break; = \ > > - _cmp =3D __strncmp(_str, _expectedval, EXPECTED_STRSIZE= ); \ > > + _cmp =3D bpf_strncmp(_str, EXPECTED_STRSIZE, _expectedv= al); \ >=20 > Though it's equivalent, the point of the test is to be heavy > for the verifier with open coded __strncmp(). >=20 > pw-bot: cr I double checked that before acking, the test was added as a part of [1]. So it seems to be focused on bpf_snprintf_btf(), not on scalability. And it's not that heavy in terms of instructions budget: File Program Verdict Insns States ----------------------- ----------------------- ------- ----- ------ netif_receive_skb.bpf.o trace_netif_receive_skb success 18152 629 [1] https://lore.kernel.org/bpf/1601292670-1616-5-git-send-email-alan.magui= re@oracle.com/