Re: [PATCH bpf-next v3 02/15] selftests/bpf: Add a test for an __int128 by-value argument

[Yonghong Song <yonghong.song@linux.dev>]

On 9/11/26 9:47 AM, bot+bpf-ci@kernel.org wrote:
>> diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c
>> index f7f94ccebce2..3c7ded537314 100644
>> --- a/tools/testing/selftests/bpf/prog_tests/verifier.c
>> +++ b/tools/testing/selftests/bpf/prog_tests/verifier.c
>> @@ -5,6 +5,7 @@
>>   #include "arena_kfunc.skel.h"
>>   #include "arena_kfunc_jit.skel.h"
>>   #include "cap_helpers.h"
>> +#include "verifier_aggregate_arg.skel.h"
>>   #include "verifier_aggregate_ret.skel.h"
>>   #include "verifier_align.skel.h"
>>   #include "verifier_and.skel.h"
>> @@ -171,6 +172,7 @@ void test_arena_kfunc(void)                   { RUN_TESTS(arena_kfunc); }
>>
>>   void test_arena_kfunc_jit(void)               { RUN_TESTS(arena_kfunc_jit); }
>>
>> +void test_verifier_aggregate_arg(void)        { RUN_TESTS(verifier_aggregate_arg); }
>>   void test_verifier_aggregate_ret(void)        { RUN_TESTS(verifier_aggregate_ret); }
>>   void test_verifier_align(void)                { RUN(verifier_align); }
>>   void test_verifier_and(void)                  { RUN(verifier_and); }
>> diff --git a/tools/testing/selftests/bpf/progs/verifier_aggregate_arg.c b/tools/testing/selftests/bpf/progs/verifier_aggregate_arg.c
>> new file mode 100644
>> index 000000000000..d90f754396d0
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/progs/verifier_aggregate_arg.c
>> @@ -0,0 +1,40 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */
>> +#include <vmlinux.h>
>> +#include <bpf/bpf_helpers.h>
>> +#include "bpf_misc.h"
>> +
>> +#define MIX_A	0xdeadbeefcafef00dULL
>> +#define MIX_B	0x0123456789abcdefULL
>> +
>> +#ifdef __SIZEOF_INT128__
>> +
>> +typedef unsigned __int128 u128;
>> +
>> +__noinline __u64 take_i128_global(int a, u128 v, int c)
>> +{
>> +	return (__u64)a + (__u64)(v >> 64) + (__u64)v + c;
>> +}
>> +
>> +SEC("tc")
>> +/*
>> + * The verifier counts one argument register for the __int128 and marks only
>> + * R1 through R3 at the entry of take_i128_global(), while the compiler passed
>> + * a in R1, v in R2:R3 and c in R4.
>> + */
>> +__failure __msg("R4 !read_ok")
>> +int aggregate_arg_int128_c_test(struct __sk_buff *skb)
>> +{
>> +	__u64 a = skb->len ^ MIX_A;
>> +	__u64 b = skb->len ^ MIX_B;
>> +	u128 v = ((u128)a << 64) | b;
>> +
>> +	if (take_i128_global(1, v, 2) != a + b + 3)
>> +		return 1;
>> +
>> +	return 0;
>> +}
>> +
>> +#endif /* __SIZEOF_INT128__ */
>> +
>> +char _license[] SEC("license") = "GPL";
> A subsystem pattern flags this as potentially concerning: every program
> in the new file is wrapped in '#ifdef __SIZEOF_INT128__' with no '#else'
> branch.
>
> When a BPF compiler does not define __SIZEOF_INT128__ (for example, when
> building with bpf-gcc via BPF_GCC=1), the generated verifier_aggregate_arg.bpf.o
> contains no programs at all. The skeleton still compiles because bpftool
> guards maps/progs/links members on their counts, but test_loader__run_subtests()
> then iterates zero programs and test_progs.c reports the test as passing with
> no indication that the __int128 coverage was compiled out.
>
> Every sibling prog file in progs/ that wraps all of its tests in a feature
> #ifdef adds an '#else' dummy carrying __description()/__skip() so the result
> is a visible SKIP instead. For instance, verifier_aggregate_ret.c (from the
> same series) includes such a dummy at lines 167-175 with the message "needs
> LLVM 23, dummy test". The same pattern appears in verifier_gotol.c,
> verifier_bswap.c, verifier_ldsx.c, verifier_movsx.c, verifier_sdiv.c,
> verifier_private_stack.c, verifier_stack_arg_order.c, verifier_load_acquire.c,
> verifier_store_release.c, arena_kfunc.c, stack_arg_precision.c, and
> stack_arg_fail.c.
>
> Should this file include an '#else' dummy with __skip() to match the
> pattern used by its sibling tests, so that builds without __SIZEOF_INT128__
> report SKIP rather than silently passing?
>
> Note: __SIZEOF_INT128__ is defined by every clang for the bpf target, so
> the normal CI matrix (clang test_progs, no_alu32, cpuv4) does compile and
> run the test. Only the optional bpf-gcc flavor would be affected.

This should be okay. Later selftest will have more contents in file verifier_aggregate_arg.c
which has some not-guarded bpf programs.

>
>
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
>
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/34620351527