From: Yonghong Song <yonghong.song@linux.dev>
To: bot+bpf-ci@kernel.org, bpf@vger.kernel.org
Cc: ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net,
eddyz87@gmail.com, kernel-team@fb.com, martin.lau@kernel.org,
mason@kernel.org, ihor.solodrai@linux.dev
Subject: Re: [PATCH bpf-next 03/12] bpf: Support by-value struct arguments up to 16 bytes
Date: Mon, 7 Sep 2026 21:19:16 -0700 [thread overview]
Message-ID: <f552724f-e978-4cb4-a4c9-3069eb170027@linux.dev> (raw)
In-Reply-To: <b138867c4eb9919dddb35a674224d5346c809970749a5a52f378fbc3ad19e376@mail.kernel.org>
On 9/3/26 11:09 PM, bot+bpf-ci@kernel.org wrote:
>> A global function taking a struct or union by value is rejected today:
>>
>> Arg#1 type STRUCT in tar() is not supported yet.
>>
>> A struct of at most 16 bytes arrives in one or two consecutive
>> registers. Currently, the struct is composed of scalars.
>>
>> The slots of a value are independent of each other, so the compiler may
>> split one across the last argument register and the stack, as in
>>
>> static void f(int a, int b, int c, int d, struct pair p);
>>
>> or place it wholly past the registers, and the verifier describes either
>> the same way. What has to follow the slots is stack_arg_cnt, recomputed
>> from the slots consumed, together with the "no stack args in global
>> functions" and JIT support checks.
> This isn't a bug, but could the wording be more precise? The phrase
> "Currently, the struct is composed of scalars" reads as a statement of
> fact about a particular struct, but the code enforces it as a requirement
> on every by-value argument through btf_struct_is_composed_of() in
> btf_prepare_func_args(). Would it help to say that only scalar-composed
> structs are accepted for now?
Okay, will clarify in the commit message.
>
> Also, the changelog doesn't mention that sub->arg_cnt changes meaning from
> the BTF parameter count to the argument-slot count, which is the reason
> the kernel/bpf/verifier.c hunk is needed at all. Would noting this change
> help reviewers understand the verifier.c modification?
>
>
> ---
> 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/33840714551
next prev parent reply other threads:[~2026-09-08 4:19 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-04 5:09 [PATCH bpf-next 00/12] bpf: Support by-value struct and __int128 arguments Yonghong Song
2026-09-04 5:10 ` [PATCH bpf-next 01/12] selftests/bpf: Add a test for an __int128 by-value argument Yonghong Song
2026-09-04 5:10 ` [PATCH bpf-next 02/12] bpf: Index global function arguments by argument slot Yonghong Song
2026-09-04 5:10 ` [PATCH bpf-next 03/12] bpf: Support by-value struct arguments up to 16 bytes Yonghong Song
2026-09-04 5:23 ` sashiko-bot
2026-09-08 4:17 ` Yonghong Song
2026-09-04 6:09 ` bot+bpf-ci
2026-09-08 4:19 ` Yonghong Song [this message]
2026-09-04 5:10 ` [PATCH bpf-next 04/12] bpf: Support __int128 as a by-value function argument Yonghong Song
2026-09-04 5:32 ` sashiko-bot
2026-09-08 4:20 ` Yonghong Song
2026-09-04 6:09 ` bot+bpf-ci
2026-09-08 4:21 ` Yonghong Song
2026-09-04 5:10 ` [PATCH bpf-next 05/12] bpf: Support by-value struct and __int128 kfunc arguments Yonghong Song
2026-09-04 6:18 ` sashiko-bot
2026-09-08 4:22 ` Yonghong Song
2026-09-04 6:24 ` bot+bpf-ci
2026-09-08 4:23 ` Yonghong Song
2026-09-04 5:10 ` [PATCH bpf-next 06/12] bpf: Add a JIT helper for the outgoing stack of kfunc calls Yonghong Song
2026-09-04 5:25 ` sashiko-bot
2026-09-08 4:26 ` Yonghong Song
2026-09-04 5:10 ` [PATCH bpf-next 07/12] bpf, x86: Place kfunc arguments per the SysV calling convention Yonghong Song
2026-09-04 5:36 ` sashiko-bot
2026-09-08 4:27 ` Yonghong Song
2026-09-04 23:58 ` Alexei Starovoitov
2026-09-06 20:15 ` Yonghong Song
2026-09-08 4:33 ` Alexei Starovoitov
2026-09-08 5:02 ` Yonghong Song
2026-09-08 5:10 ` Yonghong Song
2026-09-08 15:24 ` Alexei Starovoitov
2026-09-08 18:43 ` Yonghong Song
2026-09-09 1:59 ` Alexei Starovoitov
2026-09-04 5:10 ` [PATCH bpf-next 08/12] bpf: Record a 16-byte argument alignment in the function model Yonghong Song
2026-09-04 6:09 ` bot+bpf-ci
2026-09-08 4:28 ` Yonghong Song
2026-09-04 5:10 ` [PATCH bpf-next 09/12] bpf, arm64: Place kfunc arguments per AAPCS64 Yonghong Song
2026-09-04 6:09 ` bot+bpf-ci
2026-09-04 5:10 ` [PATCH bpf-next 10/12] selftests/bpf: Add C tests for by-value arguments up to 16 bytes Yonghong Song
2026-09-04 5:19 ` sashiko-bot
2026-09-08 4:33 ` Yonghong Song
2026-09-04 6:09 ` bot+bpf-ci
2026-09-08 4:34 ` Yonghong Song
2026-09-04 5:10 ` [PATCH bpf-next 11/12] selftests/bpf: Add inline-asm tests for by-value arguments Yonghong Song
2026-09-04 6:09 ` bot+bpf-ci
2026-09-08 4:35 ` Yonghong Song
2026-09-04 5:11 ` [PATCH bpf-next 12/12] selftests/bpf: Add tests for by-value kfunc arguments Yonghong Song
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