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Thu, 09 Jul 2026 18:19:59 -0700 (PDT) Message-ID: Subject: Re: [PATCH bpf-next 09/12] selftests/bpf: Add C tests for 16-byte returns in R0:R2 From: Eduard Zingerman To: Yonghong Song , bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , kernel-team@fb.com Date: Thu, 09 Jul 2026 18:19:56 -0700 In-Reply-To: <20260708201025.2160583-1-yonghong.song@linux.dev> References: <20260708200939.2153664-1-yonghong.song@linux.dev> <20260708201025.2160583-1-yonghong.song@linux.dev> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2-10 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2026-07-08 at 13:10 -0700, Yonghong Song wrote: > Add selftests that exercise a 16-byte return value passed in the R0:R2 > register pair, expressed in C so they rely on the compiler lowering the > register-pair return. Tests include an __int128 return (from a subprogram > and a kfunc), a 16-byte struct return (from static and global subprograms > and a kfunc) and a 16-byte union return. >=20 > The R0:R2 return convention is only emitted by LLVM 23 and newer, so the > programs are gated on __clang_major__ >=3D 23; with an older compiler the= y > return a sentinel and the "int128_c", "struct_c", "global_struct_c", > "kfunc_struct_c" and "union_c" subtests are skipped. >=20 > Signed-off-by: Yonghong Song > --- [...] > +static void run_prog(struct bpf_program *prog, bool may_skip) > +{ > + char buf[64] =3D {}; > + LIBBPF_OPTS(bpf_test_run_opts, topts, > + .data_in =3D buf, > + .data_size_in =3D sizeof(buf), > + .repeat =3D 1, > + ); > + int err; > + > + err =3D bpf_prog_test_run_opts(bpf_program__fd(prog), &topts); > + if (!ASSERT_OK(err, "test_run")) > + return; > + > + if (may_skip && (int)topts.retval =3D=3D -1) { > + test__skip(); > + return; > + } > + > + ASSERT_EQ(topts.retval, 0, "aggregate_ret_result"); > +} > + > +void test_aggregate_ret(void) > +{ The test_aggregate_ret()/run_prog() duplicate functionality provided by the __retval tag from test_loader.c. To achieve the same skipping mechanics I suggest to: - extend test_loader.c / bpf_misc.h with a new tag: __skip("reason") - use this tag as: #ifdef __clang_major__ >=3D 23 SEC("tc") int aggregate_ret_test(struct __sk_buff *skb) { ... } #else SEC("tc") __skip("... need clang23 ...") int aggregate_ret_test(struct __sk_buff *skb) { ... } #endif [...] > diff --git a/tools/testing/selftests/bpf/progs/aggregate_ret_int128_c.c .= .. > diff --git a/tools/testing/selftests/bpf/progs/aggregate_ret_struct_c.c .= .. > diff --git a/tools/testing/selftests/bpf/progs/aggregate_ret_union_c.c ..= . Nit: all three files can be merged into one. [...]