arch-arm: Fix incorrect assumptions in ELIs64

The state of EL1 wasn't determined correctly when running in secure
mode if virtualisation was enabled. This changset updates the
implementation to match the canonical behavior from the ARM ARM.

Change-Id: I7ed6f5c003617773603f678667aac069d73b6f62
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/7141
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>

2 files changed, 41 insertions, 27 deletions

diff --git a/src/arch/arm/utility.cc b/src/arch/arm/utility.cc
index b26564c61..56503ac62 100644
--- a/src/arch/arm/utility.cc
+++ b/src/arch/arm/utility.cc
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009-2014, 2016 ARM Limited
+ * Copyright (c) 2009-2014, 2016-2017 ARM Limited
  * All rights reserved.
  *
  * The license below extends only to copyright in the software and shall
@@ -230,33 +230,45 @@ getMPIDR(ArmSystem *arm_sys, ThreadContext *tc)
 bool
 ELIs64(ThreadContext *tc, ExceptionLevel el)
 {
-    if (ArmSystem::highestEL(tc) == el)
-        // Register width is hard-wired
-        return ArmSystem::highestELIs64(tc);
+    return !ELIs32(tc, el);
+}
 
-    switch (el) {
-      case EL0:
-        return opModeIs64(currOpMode(tc));
-      case EL1:
-        {
-            if (ArmSystem::haveVirtualization(tc)) {
-                HCR hcr = tc->readMiscReg(MISCREG_HCR_EL2);
-                return hcr.rw;
-            } else if (ArmSystem::haveSecurity(tc)) {
-                SCR scr = tc->readMiscReg(MISCREG_SCR_EL3);
-                return scr.rw;
-            }
-            panic("must haveSecurity(tc)");
-        }
-      case EL2:
-        {
-            assert(ArmSystem::haveSecurity(tc));
-            SCR scr = tc->readMiscReg(MISCREG_SCR_EL3);
-            return scr.rw;
+bool
+ELIs32(ThreadContext *tc, ExceptionLevel el)
+{
+    // Return true if the specified EL is in aarch32 state.
+
+    const bool have_el3 = ArmSystem::haveSecurity(tc);
+    const bool have_el2 = ArmSystem::haveVirtualization(tc);
+
+    panic_if(el == EL2 && !have_el2, "Asking for EL2 when it doesn't exist");
+    panic_if(el == EL3 && !have_el3, "Asking for EL3 when it doesn't exist");
+
+    if (ArmSystem::highestELIs64(tc)
+              && ArmSystem::highestEL(tc) == el) {
+        return false;
+    } else if (!ArmSystem::highestELIs64(tc)) {
+        // All levels are using AArch32
+        return true;
+    } else {
+        SCR scr = tc->readMiscReg(MISCREG_SCR_EL3);
+        bool aarch32_below_el3 = (have_el3 && scr.rw == 0);
+
+        HCR hcr = tc->readMiscReg(MISCREG_HCR_EL2);
+        bool aarch32_at_el1 = (aarch32_below_el3
+                                || (have_el2
+                                && !inSecureState(tc) && hcr.rw == 0));
+
+        // Only know if EL0 using AArch32 from PSTATE
+        if (el == EL0 && !aarch32_at_el1) {
+            CPSR cpsr = tc->readMiscReg(MISCREG_CPSR);
+            panic_if(cpsr.el != EL0, "EL0 state is UNKNOWN");
+            // EL0 controlled by PSTATE
+            return cpsr.width != 0;
+        } else {
+            return (aarch32_below_el3 && el != EL3)
+                     || (aarch32_at_el1 && (el == EL0 || el == EL1) );
         }
-      default:
-        panic("Invalid exception level");
-        break;
     }
 }
 
diff --git a/src/arch/arm/utility.hh b/src/arch/arm/utility.hh
index 640ba70d2..622fd1282 100644
--- a/src/arch/arm/utility.hh
+++ b/src/arch/arm/utility.hh
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2010, 2012-2013, 2016 ARM Limited
+ * Copyright (c) 2010, 2012-2013, 2016-2017 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -157,6 +157,8 @@ currEL(ThreadContext *tc)
     return (ExceptionLevel) (uint8_t) cpsr.el;
 }
 
+bool ELIs32(ThreadContext *tc, ExceptionLevel el);
+
 bool ELIs64(ThreadContext *tc, ExceptionLevel el);
 
 bool isBigEndian64(ThreadContext *tc);