target-microblaze: Allow the stack protection to be disabled

Microblaze stack protection is configurable and isn't always enabled.
This patch allows the stack protection to be disabled from the
CPU properties.
Signed-off-by: NAlistair Francis <alistair.francis@xilinx.com>
Signed-off-by: NEdgar E. Iglesias <edgar.iglesias@xilinx.com>

target-microblaze/cpu-qom.h

@@ -59,6 +59,11 @@ typedef struct MicroBlazeCPU {
     uint32_t base_vectors;
     /*< public >*/
 
+    /* Microblaze Configuration Settings */
+    struct {
+        bool stackprot;
+    } cfg;
+
     CPUMBState env;
 } MicroBlazeCPU;
 

target-microblaze/cpu.c

@@ -114,6 +114,9 @@ static void mb_cpu_realizefn(DeviceState *dev, Error **errp)
                         | PVR2_USE_FPU2_MASK \
                         | PVR2_FPU_EXC_MASK \
                         | 0;
+
+    env->pvr.regs[0] |= cpu->cfg.stackprot ? PVR0_SPROT_MASK : 0;
+
     env->pvr.regs[10] = 0x0c000000; /* Default to spartan 3a dsp family.  */
     env->pvr.regs[11] = PVR11_USE_MMU | (16 << 17);
 
@@ -156,6 +159,8 @@ static const VMStateDescription vmstate_mb_cpu = {
 
 static Property mb_properties[] = {
     DEFINE_PROP_UINT32("xlnx.base-vectors", MicroBlazeCPU, base_vectors, 0),
+    DEFINE_PROP_BOOL("use-stack-protection", MicroBlazeCPU, cfg.stackprot,
+                     true),
     DEFINE_PROP_END_OF_LIST(),
 };
 

target-microblaze/cpu.h

@@ -128,6 +128,7 @@ typedef struct CPUMBState CPUMBState;
 #define PVR0_FAULT			0x00100000
 #define PVR0_VERSION_MASK               0x0000FF00
 #define PVR0_USER1_MASK                 0x000000FF
+#define PVR0_SPROT_MASK                 0x00000001
 
 /* User 2 PVR mask */
 #define PVR1_USER2_MASK                 0xFFFFFFFF

target-microblaze/translate.c

@@ -862,7 +862,7 @@ static inline TCGv *compute_ldst_addr(DisasContext *dc, TCGv *t)
     int stackprot = 0;
 
     /* All load/stores use ra.  */
-    if (dc->ra == 1) {
+    if (dc->ra == 1 && dc->cpu->cfg.stackprot) {
         stackprot = 1;
     }
 
@@ -875,7 +875,7 @@ static inline TCGv *compute_ldst_addr(DisasContext *dc, TCGv *t)
             return &cpu_R[dc->ra];
         }
 
-        if (dc->rb == 1) {
+        if (dc->rb == 1 && dc->cpu->cfg.stackprot) {
             stackprot = 1;
         }