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([2620:10d:c092:500::6:c4f]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-488fb75a913sm87010685e9.12.2026.04.20.04.48.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Apr 2026 04:48:11 -0700 (PDT) Message-ID: Date: Mon, 20 Apr 2026 12:48:10 +0100 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 bpf-next 6/6] Documentation/bpf: Update btf doc with updated vlen, kind sizes To: Alan Maguire , bot+bpf-ci@kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org Cc: martin.lau@linux.dev, eddyz87@gmail.com, memxor@gmail.com, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, qmo@kernel.org, bpf@vger.kernel.org, martin.lau@kernel.org, clm@meta.com, ihor.solodrai@linux.dev References: <20260417143023.1551481-7-alan.maguire@oracle.com> <0c04590254c3cf4a4a53803c5c8d613bf2ad288b3eaf2a641794f78d4bf0d5c9@mail.kernel.org> <4c95e885-1b21-4e25-b9c5-b6a2c37bcf1c@oracle.com> Content-Language: en-US From: Mykyta Yatsenko In-Reply-To: <4c95e885-1b21-4e25-b9c5-b6a2c37bcf1c@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 4/20/26 9:09 AM, Alan Maguire wrote: > On 17/04/2026 16:39, bot+bpf-ci@kernel.org wrote: >>> diff --git a/Documentation/bpf/btf.rst b/Documentation/bpf/btf.rst >>> index 3b60583f5db2..3f05f17990ad 100644 >>> --- a/Documentation/bpf/btf.rst >>> +++ b/Documentation/bpf/btf.rst >>> @@ -97,10 +97,8 @@ Each type contains the following common data:: >>> struct btf_type { >>> __u32 name_off; >>> /* "info" bits arrangement >>> - * bits 0-15: vlen (e.g. # of struct's members) >>> - * bits 16-23: unused >>> - * bits 24-28: kind (e.g. int, ptr, array...etc) >>> - * bits 29-30: unused >>> + * bits 0-23: vlen (e.g. # of struct's members) >>> + * bits 24-30: kind (e.g. int, ptr, array...etc) >> >> Does the kind field documentation accurately match the UAPI implementation? >> The UAPI defines BTF_INFO_KIND as: >> >> #define BTF_INFO_KIND(info) (((info) >> 24) & 0x7f) >> >> The mask 0x7f is 7 bits, which means kind occupies bits 24-30. This >> documentation shows "bits 24-30" which appears correct. >> >> However, checking the actual implementation confirms the kind field uses >> only 7 bits (0x7f mask), leaving bit 31 exclusively for kind_flag. >> > > maybe I'm misreading this (I've reread it several times) but I think the AI has > misfired here; it's seems be questioning whether the docs match the UAPI change > while at the same time confirming they match the UAPI change. Again I may be > missing something... > Yes, it looks like it did not properly see -/+ and messed up what was added/deleted. >> >> Should the documentation have removed the "bits 16-23: unused" description? >> The previous documentation listed bits 16-23 as unused, but after expanding >> vlen to bits 0-23, these bits are now part of vlen. The current bit >> allocation is: >> >> - Bits 0-23: vlen (24 bits) >> - Bits 24-30: kind (7 bits) >> - Bit 31: kind_flag (1 bit) >> >> The patch removes the "bits 16-23: unused" line from the struct comment, >> which correctly reflects that these bits are now part of the expanded vlen >> field. >> >>> * bit 31: kind_flag, currently used by >>> * struct, union, enum, fwd, enum64, >>> * decl_tag and type_tag >> >> >> --- >> 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/24570998051 >