arch-arm: Fix AArch32 SETEND Instruction

This patch fixes AArch32 SETEND instruction, which was previously
executed unconditionally without checking (H)SCTLR.SED field. This bit
enables/disables the trapping of the instruction.

Change-Id: Ib3d2194c8d16c34ec2a9ab3e8090081900c1e42e
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/7981
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

2 files changed, 120 insertions, 2 deletions

diff --git a/src/arch/arm/insts/static_inst.cc b/src/arch/arm/insts/static_inst.cc
index 61f31e5db..f7a9745ad 100644
--- a/src/arch/arm/insts/static_inst.cc
+++ b/src/arch/arm/insts/static_inst.cc
@@ -859,6 +859,77 @@ ArmStaticInst::trapWFx(ThreadContext *tc,
     return fault;
 }
 
+Fault
+ArmStaticInst::checkSETENDEnabled(ThreadContext *tc, CPSR cpsr) const
+{
+    bool setend_disabled(false);
+    ExceptionLevel pstateEL = (ExceptionLevel)(uint8_t)(cpsr.el);
+
+    if (pstateEL == EL2) {
+       setend_disabled = ((SCTLR)tc->readMiscRegNoEffect(MISCREG_HSCTLR)).sed;
+    } else {
+        // Please note: in the armarm pseudocode there is a distinction
+        // whether EL1 is aarch32 or aarch64:
+        // if ELUsingAArch32(EL1) then SCTLR.SED else SCTLR[].SED;
+        // Considering that SETEND is aarch32 only, ELUsingAArch32(EL1)
+        // will always be true (hence using SCTLR.SED) except for
+        // instruction executed at EL0, and with an AArch64 EL1.
+        // In this case SCTLR_EL1 will be used. In gem5 the register is
+        // mapped to SCTLR_ns. We can safely use SCTLR and choose the
+        // appropriate bank version.
+
+        // Get the index of the banked version of SCTLR:
+        // SCTLR_s or SCTLR_ns.
+        auto banked_sctlr = flattenMiscRegNsBanked(
+            MISCREG_SCTLR, tc, !inSecureState(tc));
+
+        // SCTLR.SED bit is enabling/disabling the ue of SETEND instruction.
+        setend_disabled = ((SCTLR)tc->readMiscRegNoEffect(banked_sctlr)).sed;
+    }
+
+    return setend_disabled ? undefinedFault32(tc, pstateEL) :
+                             NoFault;
+}
+
+Fault
+ArmStaticInst::undefinedFault32(ThreadContext *tc,
+                                ExceptionLevel pstateEL) const
+{
+    // Even if we are running in aarch32, the fault might be dealt with in
+    // aarch64 ISA.
+    if (generalExceptionsToAArch64(tc, pstateEL)) {
+        return undefinedFault64(tc, pstateEL);
+    } else {
+        // Please note: according to the ARM ARM pseudocode we should handle
+        // the case when EL2 is aarch64 and HCR.TGE is 1 as well.
+        // However this case is already handled by the routeToHyp method in
+        // ArmFault class.
+        return std::make_shared<UndefinedInstruction>(
+            machInst, 0,
+            EC_UNKNOWN, mnemonic);
+    }
+}
+
+Fault
+ArmStaticInst::undefinedFault64(ThreadContext *tc,
+                                ExceptionLevel pstateEL) const
+{
+    switch (pstateEL) {
+      case EL0:
+      case EL1:
+        return std::make_shared<SupervisorTrap>(machInst, 0, EC_UNKNOWN);
+      case EL2:
+        return std::make_shared<HypervisorTrap>(machInst, 0, EC_UNKNOWN);
+      case EL3:
+        return std::make_shared<SecureMonitorTrap>(machInst, 0, EC_UNKNOWN);
+      default:
+        panic("Unrecognized Exception Level: %d\n", pstateEL);
+        break;
+    }
+
+    return NoFault;
+}
+
 static uint8_t
 getRestoredITBits(ThreadContext *tc, CPSR spsr)
 {
@@ -981,6 +1052,18 @@ ArmStaticInst::getPSTATEFromPSR(ThreadContext *tc, CPSR cpsr, CPSR spsr) const
     return new_cpsr;
 }
 
+bool
+ArmStaticInst::generalExceptionsToAArch64(ThreadContext *tc,
+                                          ExceptionLevel pstateEL) const
+{
+    // Returns TRUE if exceptions normally routed to EL1 are being handled
+    // at an Exception level using AArch64, because either EL1 is using
+    // AArch64 or TGE is in force and EL2 is using AArch64.
+    HCR hcr = ((HCR)tc->readMiscReg(MISCREG_HCR_EL2));
+    return (pstateEL == EL0 && !ELIs32(tc, EL1)) ||
+           (ArmSystem::haveEL(tc, EL2) && !inSecureState(tc) &&
+               !ELIs32(tc, EL2) && hcr.tge);
+}
 
 
 }
diff --git a/src/arch/arm/insts/static_inst.hh b/src/arch/arm/insts/static_inst.hh
index 9aed77c21..c68880c97 100644
--- a/src/arch/arm/insts/static_inst.hh
+++ b/src/arch/arm/insts/static_inst.hh
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2010-2013,2016-2017 ARM Limited
+ * Copyright (c) 2010-2013,2016-2018 ARM Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -434,14 +434,49 @@ class ArmStaticInst : public StaticInst
     Fault trapWFx(ThreadContext *tc, CPSR cpsr, SCR scr, bool isWfe) const;
 
     /**
+     * Check if SETEND instruction execution in aarch32 should be trapped.
+     *
+     * See aarch32/exceptions/traps/AArch32.CheckSETENDEnabled in the
+     * ARM ARM pseudocode library.
+     */
+    Fault checkSETENDEnabled(ThreadContext *tc, CPSR cpsr) const;
+
+    /**
+     * UNDEFINED behaviour in AArch32
+     *
+     * See aarch32/exceptions/traps/AArch32.UndefinedFault in the
+     * ARM ARM pseudocode library.
+     */
+    Fault undefinedFault32(ThreadContext *tc, ExceptionLevel el) const;
+
+    /**
+     * UNDEFINED behaviour in AArch64
+     *
+     * See aarch64/exceptions/traps/AArch64.UndefinedFault in the
+     * ARM ARM pseudocode library.
+     */
+    Fault undefinedFault64(ThreadContext *tc, ExceptionLevel el) const;
+
+    /**
      * Get the new PSTATE from a SPSR register in preparation for an
      * exception return.
      *
      * See shared/functions/system/SetPSTATEFromPSR in the ARM ARM
-     * psueodcode library.
+     * pseudocode library.
      */
     CPSR getPSTATEFromPSR(ThreadContext *tc, CPSR cpsr, CPSR spsr) const;
 
+    /**
+     * Return true if exceptions normally routed to EL1 are being handled
+     * at an Exception level using AArch64, because either EL1 is using
+     * AArch64 or TGE is in force and EL2 is using AArch64.
+     *
+     * See aarch32/exceptions/exceptions/AArch32.GeneralExceptionsToAArch64
+     * in the ARM ARM pseudocode library.
+     */
+    bool generalExceptionsToAArch64(ThreadContext *tc,
+                                    ExceptionLevel pstateEL) const;
+
   public:
     virtual void
     annotateFault(ArmFault *fault) {}