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Sat, 31 Oct 2026 07:44:56 -0400 (EDT) Date: Sat, 31 Oct 2026 20:44:53 +0900 (JST) Message-Id: <20261031.204453.2065904807866384795.tomo@flapping.org> To: chenhan0017.work@gmail.com Cc: rust-for-linux@vger.kernel.org, a.hindborg@kernel.org, boqun@kernel.org, fujita.tomonori@gmail.com, frederic@kernel.org, lyude@redhat.com, tglx@kernel.org, anna-maria@linutronix.de, jstultz@google.com, sboyd@kernel.org, ojeda@kernel.org, gary@garyguo.net, bjorn3_gh@protonmail.com, lossin@kernel.org, aliceryhl@google.com, tmgross@umich.edu, dakr@kernel.org, daniel.almeida@collabora.com, tamird@kernel.org, acourbot@nvidia.com, work@onurozkan.dev, miguel.ojeda.sandonis@gmail.com, tomo@flapping.org, georgeandrout13@gmail.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v5 2/3] rust: time: make Delta division and remainder fail consistently From: FUJITA Tomonori In-Reply-To: <20261031103206.24051-3-chenhan0017.work@gmail.com> References: <20261031103206.24051-1-chenhan0017.work@gmail.com> <20261031103206.24051-3-chenhan0017.work@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit On Sat, 31 Oct 2026 18:32:05 +0800 chenhan wrote: > Delta's division and rem_nanos() use Rust operators on 64-bit and C > helpers on 32-bit. The report shows that rem_nanos(0) can return 10 for > a 10 ns dividend on ARMv7, while the same call panics on x86-64. The > i64::MIN / -1 case also differs, and neither API documents these inputs. > > Check for zero divisors and i64::MIN with -1 before the architecture- > specific code, and document the panic conditions on each method. This > matches Rust's signed division and remainder operators, including when > overflow checks are disabled. Valid-input results and API signatures > are unchanged; invalid inputs now panic on 32-bit too. > > No in-tree calls to either API were found at the base commit. The checks > stay in the existing methods so the fix does not depend on introducing > a math module. > > Fixes: 4521438fb076 ("rust: time: Implement basic arithmetic operations for Delta") > Reported-by: Georgios Androutsopoulos > Closes: https://github.com/Rust-for-Linux/linux/issues/1254 > Cc: stable@vger.kernel.org > Assisted-by: LLM > Signed-off-by: chenhan Reviewed-by: FUJITA Tomonori