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[81.2.115.148]) by smtp.gmail.com with ESMTPSA id w21sm19667319wmi.45.2020.12.15.06.12.57 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Dec 2020 06:12:57 -0800 (PST) From: Peter Maydell To: qemu-devel@nongnu.org Subject: [PULL 16/20] hw/misc/zynq_slcr: Avoid #DIV/0! error Date: Tue, 15 Dec 2020 14:12:33 +0000 Message-Id: <20201215141237.17868-17-peter.maydell@linaro.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20201215141237.17868-1-peter.maydell@linaro.org> References: <20201215141237.17868-1-peter.maydell@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::331; envelope-from=peter.maydell@linaro.org; helo=mail-wm1-x331.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=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 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" From: Philippe Mathieu-Daudé Malicious user can set the feedback divisor for the PLLs to zero, triggering a floating-point exception (SIGFPE). As the datasheet [*] is not clear how hardware behaves when these bits are zeroes, use the maximum divisor possible (128) to avoid the software FPE. [*] Zynq-7000 TRM, UG585 (v1.12.2) B.28 System Level Control Registers (slcr) -> "Register (slcr) ARM_PLL_CTRL" 25.10.4 PLLs -> "Software-Controlled PLL Update" Fixes: 38867cb7ec9 ("hw/misc/zynq_slcr: add clock generation for uarts") Reported-by: Gaoning Pan Signed-off-by: Philippe Mathieu-Daudé Reviewed-by: Alistair Francis Reviewed-by: Edgar E. Iglesias Reviewed-by: Damien Hedde Message-id: 20201210141610.884600-1-f4bug@amsat.org Signed-off-by: Peter Maydell --- hw/misc/zynq_slcr.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/hw/misc/zynq_slcr.c b/hw/misc/zynq_slcr.c index a2b28019e3c..66504a9d3ab 100644 --- a/hw/misc/zynq_slcr.c +++ b/hw/misc/zynq_slcr.c @@ -217,6 +217,11 @@ static uint64_t zynq_slcr_compute_pll(uint64_t input, uint32_t ctrl_reg) return 0; } + /* Consider zero feedback as maximum divide ratio possible */ + if (!mult) { + mult = 1 << R_xxx_PLL_CTRL_PLL_FPDIV_LENGTH; + } + /* frequency multiplier -> period division */ return input / mult; } -- 2.20.1