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[64.119.15.123]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-71908fe2441sm1454627b3a.51.2024.09.10.07.44.35 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 10 Sep 2024 07:44:35 -0700 (PDT) From: Dave Thaler X-Google-Original-From: "Dave Thaler" To: "'Yonghong Song'" , "'Alexei Starovoitov'" , "'Zac Ecob'" , "'Daniel Borkmann'" Cc: References: <1058c69c-3e2c-4c0b-b777-2b0460f443f9@linux.dev> In-Reply-To: <1058c69c-3e2c-4c0b-b777-2b0460f443f9@linux.dev> Subject: RE: Kernel oops caused by signed divide Date: Tue, 10 Sep 2024 07:44:33 -0700 Message-ID: <18d101db038f$f3c2d400$db487c00$@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 16.0 Thread-Index: AQF9UZIBIzpsIoIccFtpL0UiWnR2xwFVGHnBAkqJ6fWy738PwA== Content-Language: en-us Yonghong Song wrote: [...] > In verifier, we have > /* [R,W]x div 0 -> 0 */ > /* [R,W]x mod 0 -> [R,W]x */ > > What the value for > Rx_a sdiv Rx_b -> ? > where Rx_a = INT64_MIN and Rx_b = -1? > > Should we just do > INT64_MIN sdiv -1 -> -1 > or some other values? What happens for BPF_NEG INT64_MIN? Dave