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([2620:10d:c092:500::7:916f]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-447b3d481fdsm5771030f8f.8.2026.04.29.05.48.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 29 Apr 2026 05:48:04 -0700 (PDT) Message-ID: <006c46ba8ea2a37d0fa75f82645e2c011c72cc8a.camel@gmail.com> Subject: Re: [PATCH bpf-next 07/18] bpf: Enable r11 based insns From: Eduard Zingerman To: Yonghong Song , bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , "Jose E . Marchesi" , kernel-team@fb.com, Martin KaFai Lau Date: Wed, 29 Apr 2026 05:48:04 -0700 In-Reply-To: <20260424171509.2041667-1-yonghong.song@linux.dev> References: <20260424171433.2034470-1-yonghong.song@linux.dev> <20260424171509.2041667-1-yonghong.song@linux.dev> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.3 (3.58.3-1.fc43) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2026-04-24 at 10:15 -0700, Yonghong Song wrote: > BPF_REG_PARAMS (r11) is used for stack argument accesses and > the following are the only insns with r11 presence: > - BPF_LDX | BPF_MEM | BPF_DW (load incoming stack arg) > - BPF_STX | BPF_MEM | BPF_DW (store register to outgoing stack arg) > - BPF_ST | BPF_MEM | BPF_DW (store immediate to outgoing stack arg) >=20 > Additionally, validate offsets: loads must use positive 8-byte aligned > offsets (8, 16, ...) since they access incoming args. Stores must use > negative 8-byte aligned offsets (-8, -16, ...) since they write > outgoing args. >=20 > The LLVM compiler [1] implemented the above BPF_REG_PARAMS insns. >=20 > [1] https://github.com/llvm/llvm-project/pull/189060 >=20 > Signed-off-by: Yonghong Song > --- Acked-by: Eduard Zingerman Nit: the is_stack_arg_{st,stx,ldx} accessors I talked about earlier would have been useful here. [...]