target-arm: add banked register accessors

If EL3 is in AArch32 state certain cp registers are banked (secure and
non-secure instance). When reading or writing to coprocessor registers
the following macros can be used.

- A32_BANKED macros are used for choosing the banked register based on provided
input security argument. This macro is used to choose the bank during
translation of MRC/MCR instructions that are dependent on something other
than the current secure state.
- A32_BANKED_CURRENT macros are used for choosing the banked register based on
current secure state. This is NOT to be used for choosing the bank used
during translation as it breaks monitor mode.

If EL3 is operating in AArch64 state coprocessor registers are not
banked anymore. The macros use the non-secure instance (_ns) in this
case, which is architecturally mapped to the AArch64 EL register.

Backports commit ea30a4b824ecc3c829b70eb9999ac5457dc5790f from qemu

qemu/target-arm/cpu.h

@@ -830,6 +830,33 @@ static inline bool arm_el_is_aa64(CPUARMState *env, int el)
     return arm_feature(env, ARM_FEATURE_AARCH64);
 }
 
+/* Macros for accessing a specified CP register bank */
+#define A32_BANKED_REG_GET(_env, _regname, _secure)    \
+    ((_secure) ? (_env)->cp15._regname##_s : (_env)->cp15._regname##_ns)
+
+#define A32_BANKED_REG_SET(_env, _regname, _secure, _val)   \
+    do {                                                \
+        if (_secure) {                                   \
+            (_env)->cp15._regname##_s = (_val);            \
+        } else {                                        \
+            (_env)->cp15._regname##_ns = (_val);           \
+        }                                               \
+    } while (0)
+
+/* Macros for automatically accessing a specific CP register bank depending on
+ * the current secure state of the system.  These macros are not intended for
+ * supporting instruction translation reads/writes as these are dependent
+ * solely on the SCR.NS bit and not the mode.
+ */
+#define A32_BANKED_CURRENT_REG_GET(_env, _regname)        \
+    A32_BANKED_REG_GET((_env), _regname,                \
+                       ((!arm_el_is_aa64((_env), 3) && arm_is_secure(_env))))
+
+#define A32_BANKED_CURRENT_REG_SET(_env, _regname, _val)                       \
+    A32_BANKED_REG_SET((_env), _regname,                                    \
+                       ((!arm_el_is_aa64((_env), 3) && arm_is_secure(_env))),  \
+                       (_val))
+
 void arm_cpu_list(FILE *f, fprintf_function cpu_fprintf);
 unsigned int arm_excp_target_el(CPUState *cs, unsigned int excp_idx);