target-arm: Implement MRS (banked) and MSR (banked) instructions

Starting with the ARMv7 Virtualization Extensions, the A32 and T32
instruction sets provide instructions "MSR (banked)" and "MRS
(banked)" which can be used to access registers for a mode other
than the current one:
 * R<m>_<mode>
 * ELR_hyp
 * SPSR_<mode>

Implement the missing instructions.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Acked-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Message-id: 1456762734-23939-1-git-send-email-peter.maydell@linaro.org

1 files changed, 120 insertions, 0 deletions

diff --git a/target-arm/op_helper.c b/target-arm/op_helper.c
index 92fde0a..d626ff1 100644
--- a/target-arm/op_helper.c
+++ b/target-arm/op_helper.c
@@ -494,6 +494,126 @@ uint32_t HELPER(get_r13_banked)(CPUARMState *env, uint32_t mode)
     }
 }
 
+static void msr_mrs_banked_exc_checks(CPUARMState *env, uint32_t tgtmode,
+                                      uint32_t regno)
+{
+    /* Raise an exception if the requested access is one of the UNPREDICTABLE
+     * cases; otherwise return. This broadly corresponds to the pseudocode
+     * BankedRegisterAccessValid() and SPSRAccessValid(),
+     * except that we have already handled some cases at translate time.
+     */
+    int curmode = env->uncached_cpsr & CPSR_M;
+
+    if (curmode == tgtmode) {
+        goto undef;
+    }
+
+    if (tgtmode == ARM_CPU_MODE_USR) {
+        switch (regno) {
+        case 8 ... 12:
+            if (curmode != ARM_CPU_MODE_FIQ) {
+                goto undef;
+            }
+            break;
+        case 13:
+            if (curmode == ARM_CPU_MODE_SYS) {
+                goto undef;
+            }
+            break;
+        case 14:
+            if (curmode == ARM_CPU_MODE_HYP || curmode == ARM_CPU_MODE_SYS) {
+                goto undef;
+            }
+            break;
+        default:
+            break;
+        }
+    }
+
+    if (tgtmode == ARM_CPU_MODE_HYP) {
+        switch (regno) {
+        case 17: /* ELR_Hyp */
+            if (curmode != ARM_CPU_MODE_HYP && curmode != ARM_CPU_MODE_MON) {
+                goto undef;
+            }
+            break;
+        default:
+            if (curmode != ARM_CPU_MODE_MON) {
+                goto undef;
+            }
+            break;
+        }
+    }
+
+    return;
+
+undef:
+    raise_exception(env, EXCP_UDEF, syn_uncategorized(),
+                    exception_target_el(env));
+}
+
+void HELPER(msr_banked)(CPUARMState *env, uint32_t value, uint32_t tgtmode,
+                        uint32_t regno)
+{
+    msr_mrs_banked_exc_checks(env, tgtmode, regno);
+
+    switch (regno) {
+    case 16: /* SPSRs */
+        env->banked_spsr[bank_number(tgtmode)] = value;
+        break;
+    case 17: /* ELR_Hyp */
+        env->elr_el[2] = value;
+        break;
+    case 13:
+        env->banked_r13[bank_number(tgtmode)] = value;
+        break;
+    case 14:
+        env->banked_r14[bank_number(tgtmode)] = value;
+        break;
+    case 8 ... 12:
+        switch (tgtmode) {
+        case ARM_CPU_MODE_USR:
+            env->usr_regs[regno - 8] = value;
+            break;
+        case ARM_CPU_MODE_FIQ:
+            env->fiq_regs[regno - 8] = value;
+            break;
+        default:
+            g_assert_not_reached();
+        }
+        break;
+    default:
+        g_assert_not_reached();
+    }
+}
+
+uint32_t HELPER(mrs_banked)(CPUARMState *env, uint32_t tgtmode, uint32_t regno)
+{
+    msr_mrs_banked_exc_checks(env, tgtmode, regno);
+
+    switch (regno) {
+    case 16: /* SPSRs */
+        return env->banked_spsr[bank_number(tgtmode)];
+    case 17: /* ELR_Hyp */
+        return env->elr_el[2];
+    case 13:
+        return env->banked_r13[bank_number(tgtmode)];
+    case 14:
+        return env->banked_r14[bank_number(tgtmode)];
+    case 8 ... 12:
+        switch (tgtmode) {
+        case ARM_CPU_MODE_USR:
+            return env->usr_regs[regno - 8];
+        case ARM_CPU_MODE_FIQ:
+            return env->fiq_regs[regno - 8];
+        default:
+            g_assert_not_reached();
+        }
+    default:
+        g_assert_not_reached();
+    }
+}
+
 void HELPER(access_check_cp_reg)(CPUARMState *env, void *rip, uint32_t syndrome,
                                  uint32_t isread)
 {