target/microblaze: gdb: Fix incorrect SReg reporting

SRegs used to be reported to GDB by iterating over the SRegs array,
however we do not store them in an order that allows them to be
reported to GDB in that way.

To fix this, a simple map is used to map the register GDB wants to its
location in the SRegs array.

Signed-off-by: Joe Komlodi <komlodi@xilinx.com>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Message-Id: <1589393329-223076-3-git-send-email-komlodi@xilinx.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>

target/microblaze/gdbstub.c

@@ -25,6 +25,21 @@ int mb_cpu_gdb_read_register(CPUState *cs, GByteArray *mem_buf, int n)
 {
     MicroBlazeCPU *cpu = MICROBLAZE_CPU(cs);
     CPUMBState *env = &cpu->env;
+    /*
+     * GDB expects SREGs in the following order:
+     * PC, MSR, EAR, ESR, FSR, BTR, EDR, PID, ZPR, TLBX, TLBSX, TLBLO, TLBHI.
+     * They aren't stored in this order, so make a map.
+     * PID, ZPR, TLBx, TLBsx, TLBLO, and TLBHI aren't modeled, so we don't
+     * map them to anything and return a value of 0 instead.
+     */
+    static const uint8_t sreg_map[6] = {
+        SR_PC,
+        SR_MSR,
+        SR_EAR,
+        SR_ESR,
+        SR_FSR,
+        SR_BTR
+    };
 
     /*
      * GDB expects registers to be reported in this order:
@@ -40,15 +55,16 @@ int mb_cpu_gdb_read_register(CPUState *cs, GByteArray *mem_buf, int n)
         n -= 32;
         switch (n) {
         case 0 ... 5:
-            return gdb_get_reg32(mem_buf, env->sregs[n]);
+            return gdb_get_reg32(mem_buf, env->sregs[sreg_map[n]]);
         /* PVR12 is intentionally skipped */
         case 6 ... 17:
             n -= 6;
             return gdb_get_reg32(mem_buf, env->pvr.regs[n]);
-        case 18 ... 24:
+        case 18:
-            /* Add an offset of 6 to resume where we left off with SRegs */
+            return gdb_get_reg32(mem_buf, env->sregs[SR_EDR]);
-            n = n - 18 + 6;
+        /* Other SRegs aren't modeled, so report a value of 0 */
-            return gdb_get_reg32(mem_buf, env->sregs[n]);
+        case 19 ... 24:
+            return gdb_get_reg32(mem_buf, 0);
         case 25:
             return gdb_get_reg32(mem_buf, env->slr);
         case 26:
@@ -66,29 +82,52 @@ int mb_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
     CPUMBState *env = &cpu->env;
     uint32_t tmp;
 
+    /*
+     * GDB expects SREGs in the following order:
+     * PC, MSR, EAR, ESR, FSR, BTR, EDR, PID, ZPR, TLBX, TLBSX, TLBLO, TLBHI.
+     * They aren't stored in this order, so make a map.
+     * PID, ZPR, TLBx, TLBsx, TLBLO, and TLBHI aren't modeled, so we don't
+     * map them to anything.
+     */
+    static const uint8_t sreg_map[6] = {
+        SR_PC,
+        SR_MSR,
+        SR_EAR,
+        SR_ESR,
+        SR_FSR,
+        SR_BTR
+    };
+
     if (n > cc->gdb_num_core_regs) {
         return 0;
     }
 
     tmp = ldl_p(mem_buf);
 
+    /*
+     * GDB expects registers to be reported in this order:
+     * R0-R31
+     * PC-BTR
+     * PVR0-PVR11
+     * EDR-TLBHI
+     * SLR-SHR
+     */
     if (n < 32) {
         env->regs[n] = tmp;
     } else {
         n -= 32;
         switch (n) {
         case 0 ... 5:
-            env->sregs[n] = tmp;
+            env->sregs[sreg_map[n]] = tmp;
             break;
         /* PVR12 is intentionally skipped */
         case 6 ... 17:
             n -= 6;
             env->pvr.regs[n] = tmp;
             break;
-        case 18 ... 24:
+        /* Only EDR is modeled in these indeces, so ignore the rest */
-            /* Add an offset of 6 to resume where we left off with SRegs */
+        case 18:
-            n = n - 18 + 6;
+            env->sregs[SR_EDR] = tmp;
-            env->sregs[n] = tmp;
             break;
         case 25:
             env->slr = tmp;