[Qemu-arm] [PATCH v4] char: cadence: check baud rate generator and divider values

[P J P]

From: Prasad J Pandit <address@hidden>

The Cadence UART device emulator calculates speed by dividing the
baud rate by a 'baud rate generator' & 'baud rate divider' value.
The device specification defines these register values to be
non-zero and within certain limits. Add checks for these limits
to avoid errors like divide by zero.

Reported-by: Huawei PSIRT <address@hidden>
Signed-off-by: Prasad J Pandit <address@hidden>
---
 hw/char/cadence_uart.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

Update: remove default reset value assignment.
  -> https://lists.gnu.org/archive/html/qemu-devel/2016-10/msg07206.html

diff --git a/hw/char/cadence_uart.c b/hw/char/cadence_uart.c
index e3bc52f..4a3c4c6 100644
--- a/hw/char/cadence_uart.c
+++ b/hw/char/cadence_uart.c
@@ -1,6 +1,11 @@
 /*
  * Device model for Cadence UART
  *
+ * Reference: Xilinx Zynq 7000 reference manual
+ *   - 
http://www.xilinx.com/support/documentation/user_guides/ug585-Zynq-7000-TRM.pdf
+ *   - Chapter 19 UART Controller
+ *   - Appendix B for Register details
+ *
  * Copyright (c) 2010 Xilinx Inc.
  * Copyright (c) 2012 Peter A.G. Crosthwaite (address@hidden)
  * Copyright (c) 2012 PetaLogix Pty Ltd.
@@ -410,6 +415,16 @@ static void uart_write(void *opaque, hwaddr offset,
             break;
         }
         break;
+    case R_BRGR: /* Baud rate generator */
+        if (value >= 0x01) {
+            s->r[offset] = value & 0xFFFF;
+        }
+        break;
+    case R_BDIV:    /* Baud rate divider */
+        if (value >= 0x04) {
+            s->r[offset] = value & 0xFF;
+        }
+        break;
     default:
         s->r[offset] = value;
     }
-- 
2.7.4