linux-kernel - Re: [PATCH bpf-next v3 1/3] bpf: Add bpf_jit_supports

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Message-Id: <DG16A1T5EJWO.D9L79G1ZE8H9@linux.dev>
Date: Thu, 29 Jan 2026 23:19:19 +0800
From: "Leon Hwang" <leon.hwang@...ux.dev>
To: <bot+bpf-ci@...nel.org>, <leon.hwang@...ux.dev>, <bpf@...r.kernel.org>
Cc: <ast@...nel.org>, <daniel@...earbox.net>, <andrii@...nel.org>,
 <martin.lau@...ux.dev>, <eddyz87@...il.com>, <song@...nel.org>,
 <yonghong.song@...ux.dev>, <john.fastabend@...il.com>,
 <kpsingh@...nel.org>, <sdf@...ichev.me>, <haoluo@...gle.com>,
 <jolsa@...nel.org>, <puranjay@...nel.org>, <xukuohai@...weicloud.com>,
 <catalin.marinas@....com>, <will@...nel.org>, <shuah@...nel.org>,
 <menglong8.dong@...il.com>, <linux-arm-kernel@...ts.infradead.org>,
 <linux-kernel@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
 <kernel-patches-bot@...com>, <martin.lau@...nel.org>, <clm@...a.com>,
 <ihor.solodrai@...ux.dev>
Subject: Re: [PATCH bpf-next v3 1/3] bpf: Add bpf_jit_supports_fsession()

On Thu Jan 29, 2026 at 10:54 PM +08, bot+bpf-ci wrote:
>> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
>> index e7ff8394e0..6e0693ac72 100644
>> --- a/kernel/bpf/verifier.c
>> +++ b/kernel/bpf/verifier.c
>> @@ -24874,6 +24874,9 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
>>  	case BPF_TRACE_FENTRY:
>>  	case BPF_TRACE_FEXIT:
>>  	case BPF_TRACE_FSESSION:
>> +		if (prog->expected_attach_type == BPF_TRACE_FSESSION &&
>> +		    !bpf_jit_supports_fsession())
>> +			return -EOPNOTSUPP;
>
> This isn't a bug, but other similar bpf_jit_supports_*() checks in
> this file include a bpf_log() message before returning an error. For
> example:
>
>   bpf_jit_supports_kfunc_call() -> "JIT does not support calling kernel function"
>   bpf_jit_supports_exceptions() -> "JIT does not support calling kfunc..."
>   bpf_jit_supports_arena()      -> "JIT doesn't support arena"
>   bpf_jit_supports_private_stack() -> "Private stack not supported by jit"
>
> Should this check also include a message like "JIT does not support
> fsession" for consistency with other similar checks in the verifier?
>

That makes sense.

Let me add the log message.

Thanks,
Leon


>
> ---
> 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/21482297342
>
> AI-authorship-score: low
> AI-authorship-explanation: The commit demonstrates specific debugging context with actual test output and errno values, correct understanding of kernel BPF conventions, and follows established patterns - typical of experienced human kernel developers.
> issues-found: 1
> issue-severity-score: low
> issue-severity-explanation: Minor consistency issue - missing bpf_log() error message compared to similar checks in the same file; does not affect functionality or stability.