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Mon, 26 Oct 2026 16:51:18 -0700 (PDT) Received: from localhost ([153.61.198.241]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2eae6c9d2cesm1516215ad.65.2026.10.26.16.51.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 26 Oct 2026 16:51:18 -0700 (PDT) X-Mailing-List: bpf@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Mon, 26 Oct 2026 23:51:17 +0000 Message-Id: Cc: , , , Subject: Re: [PATCH bpf 26/81] bpf: Support BPF_REG_ARENA_SP in the verifier From: "Alexei Starovoitov" To: "Kumar Kartikeya Dwivedi" X-Mailer: aerc 0.20.1-349-gb940a4174a3e-dirty References: <20261026025943.404450-1-alexei.starovoitov@gmail.com> <20261026025943.404450-27-alexei.starovoitov@gmail.com> In-Reply-To: On Mon Oct 26, 2026 at 5:47 PM UTC, Kumar Kartikeya Dwivedi wrote: > > Some initial questions without reading the code: > How will this split stack model work with trusted objects whose > pointers on the stack are taken and passed around (dynptrs, iterators, > etc.)? dynptrs and iterators won't work in rust. No need to drag old concepts into rust ecosystem. r12 is opt-in. rust will compile with extra llvm backend flag. It's not for old C code. > Also, will this lead to miscompiled cases where ptr to ptr to trusted is > passed to supbprog as r12 relative access? (As a way for the callee to > fill a trusted pointer for the caller, etc.)? If somebody will use this flag for C code the ptr to ptr will be arena ptr and won't become trusted. Not sure I made it clear, but some rust crates need your typed-arena featur= e.