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Mon, 28 Apr 2025 00:11:49 -0700 (PDT) Received: from [192.168.0.56] ([38.34.87.7]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-73e25a6a8b7sm7495651b3a.104.2025.04.28.00.11.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Apr 2025 00:11:48 -0700 (PDT) Message-ID: Subject: Re: [PATCH RFC bpf-next 1/4] bpf: add struct largest member size in func model From: Eduard Zingerman To: Xu Kuohai , Alexis =?ISO-8859-1?Q?Lothor=E9?= , Andrii Nakryiko Cc: Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Puranjay Mohan , Catalin Marinas , Will Deacon , Mykola Lysenko , Shuah Khan , Maxime Coquelin , Alexandre Torgue , Florent Revest , Bastien Curutchet , ebpf@linuxfoundation.org, Thomas Petazzoni , bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kselftest@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com Date: Mon, 28 Apr 2025 00:11:46 -0700 In-Reply-To: <2f13f928-9148-44e0-a44c-872a3779b0ef@huaweicloud.com> References: <20250411-many_args_arm64-v1-0-0a32fe72339e@bootlin.com> <20250411-many_args_arm64-v1-1-0a32fe72339e@bootlin.com> <6b6472c3-0718-4e60-9972-c166d51962a3@huaweicloud.com> <2f13f928-9148-44e0-a44c-872a3779b0ef@huaweicloud.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250428_001149_960967_652A841A X-CRM114-Status: UNSURE ( 9.70 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 2025-04-25 at 17:23 +0800, Xu Kuohai wrote: [...] > For the two questions you mentioned, I=E2=80=99m not sure if we can acces= s DWARF attributes > at runtime. As for adding parameter locations to BTF at building time, I = think it > means we would need to record CPU-related register info in BTF, which I d= on=E2=80=99t think > is a good idea. Another option would be for pahole to check if function parameter DW_AT_locaction is placed in accordance with ABI. These flags can be recorded in a dedicated section or smth like this. Having said that, DW_AT_locaction seem to be not very reliable. E.g. for bpf_testmod.ko generated by clang 19.1.7 I don't see DW_AT_locaction specified for parameters a, b, c.