target/ppc: Update gdbstub to read SPR's CFAR, DEC, HDEC, TB-L/U

SPR's CFAR, DEC, HDEC, TB-L/U are not implemented as part of CPUPPCState.
Hence, gdbstub is not able to access them using (CPUPPCState *)env->spr[] array.
Update gdb_get_spr_reg() method to handle these SPR's specifically.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Saif Abrar <saif.abrar@linux.vnet.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

target/ppc/gdbstub.c

@@ -394,7 +394,32 @@ static int gdb_get_spr_reg(CPUPPCState *env, GByteArray *buf, int n)
     }
 
     len = TARGET_LONG_SIZE;
-    gdb_get_regl(buf, env->spr[reg]);
+
+    /* Handle those SPRs that are not part of the env->spr[] array */
+    target_ulong val;
+    switch (reg) {
+#if defined(TARGET_PPC64)
+    case SPR_CFAR:
+        val = env->cfar;
+        break;
+#endif
+    case SPR_HDEC:
+        val = cpu_ppc_load_hdecr(env);
+        break;
+    case SPR_TBL:
+        val = cpu_ppc_load_tbl(env);
+        break;
+    case SPR_TBU:
+        val = cpu_ppc_load_tbu(env);
+        break;
+    case SPR_DECR:
+        val = cpu_ppc_load_decr(env);
+        break;
+    default:
+        val = env->spr[reg];
+    }
+    gdb_get_regl(buf, val);
+
     ppc_maybe_bswap_register(env, gdb_get_reg_ptr(buf, len), len);
     return len;
 }
@@ -411,7 +436,18 @@ static int gdb_set_spr_reg(CPUPPCState *env, uint8_t *mem_buf, int n)
 
     len = TARGET_LONG_SIZE;
     ppc_maybe_bswap_register(env, mem_buf, len);
-    env->spr[reg] = ldn_p(mem_buf, len);
+
+    /* Handle those SPRs that are not part of the env->spr[] array */
+    target_ulong val = ldn_p(mem_buf, len);
+    switch (reg) {
+#if defined(TARGET_PPC64)
+    case SPR_CFAR:
+        env->cfar = val;
+        break;
+#endif
+    default:
+        env->spr[reg] = val;
+    }
 
     return len;
 }