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[80.187.86.152]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b72bf9bcd59sm760049666b.53.2025.11.09.02.37.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 09 Nov 2025 02:37:44 -0800 (PST) Message-ID: <71950c1c-f3d4-4395-ab43-4bf1178a8acc@linaro.org> Date: Sun, 9 Nov 2025 11:37:41 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] hw/misc/npcm_clk: Don't divide by zero when calculating frequency Content-Language: en-US To: Peter Maydell , qemu-arm@nongnu.org, qemu-devel@nongnu.org Cc: Tyrone Ting , Hao Wu References: <20251107150137.1353532-1-peter.maydell@linaro.org> From: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= In-Reply-To: <20251107150137.1353532-1-peter.maydell@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::62b; envelope-from=philmd@linaro.org; helo=mail-ej1-x62b.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 7/11/25 16:01, Peter Maydell wrote: > If the guest misprograms the PLL registers to request a zero > divisor, we currently fall over with a division by zero: > > ../../hw/misc/npcm_clk.c:221:14: runtime error: division by zero > SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior ../../hw/misc/npcm_clk.c:221:14 > > Thread 1 "qemu-system-aar" received signal SIGFPE, Arithmetic exception. > 0x00005555584d8f6d in npcm7xx_clk_update_pll (opaque=0x7fffed159a20) at ../../hw/misc/npcm_clk.c:221 > 221 freq /= PLLCON_INDV(con) * PLLCON_OTDV1(con) * PLLCON_OTDV2(con); > > Avoid this by treating this invalid setting like a stopped clock > (setting freq to 0). > > Cc: qemu-stable@nongnu.org > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/549 > Signed-off-by: Peter Maydell > --- > hw/misc/npcm_clk.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) Reviewed-by: Philippe Mathieu-Daudé