arch-arm: Don't change PSTATE in Illegal Exception return

This patch fixes the Illegal Exception return handler. According to the
armarm documentation, when PSTATE.IL is set to one because of an illegal
exception return, PSTATE.{EL, nRW, SP} are unchanged. This means the
Exception level, Execution state, and stack pointer selection do not
change as a result of the return.

Change-Id: I35f2fe68fb2822a54fc4a21930871eab7a1aaab4
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/8021
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

diff --git a/src/arch/arm/insts/static_inst.cc b/src/arch/arm/insts/static_inst.cc
index aace1de2b05bfb4846002fdf0ab588e60353d6a9..a7ba91e03ed42acddbe62cce7c4e8ab4f253db71 100644 (file)
--- a/src/arch/arm/insts/static_inst.cc
+++ b/src/arch/arm/insts/static_inst.cc
@@ -1018,7 +1018,17 @@ ArmStaticInst::getPSTATEFromPSR(ThreadContext *tc, CPSR cpsr, CPSR spsr) const
     new_cpsr.ss = 0;
 
     if (illegalExceptionReturn(tc, cpsr, spsr)) {
+        // If the SPSR specifies an illegal exception return,
+        // then PSTATE.{M, nRW, EL, SP} are unchanged and PSTATE.IL
+        // is set to 1.
         new_cpsr.il = 1;
+        if (cpsr.width) {
+            new_cpsr.mode = cpsr.mode;
+        } else {
+            new_cpsr.width = cpsr.width;
+            new_cpsr.el = cpsr.el;
+            new_cpsr.sp = cpsr.sp;
+        }
     } else {
         new_cpsr.il = spsr.il;
         if (spsr.width && badMode32((OperatingMode)(uint8_t)spsr.mode)) {

diff --git a/src/arch/arm/isa.cc b/src/arch/arm/isa.cc
index c917abacf408f5d3f70660d14ad2fbab9ccebdaf..5d34e188a08da90f79b86b51e9367a7f87ad65b3 100644 (file)
--- a/src/arch/arm/isa.cc
+++ b/src/arch/arm/isa.cc
@@ -726,7 +726,7 @@ ISA::setMiscReg(int misc_reg, const MiscReg &val, ThreadContext *tc)
         CPSR old_cpsr = miscRegs[MISCREG_CPSR];
         int old_mode = old_cpsr.mode;
         CPSR cpsr = val;
-        if (old_mode != cpsr.mode) {
+        if (old_mode != cpsr.mode || cpsr.il != old_cpsr.il) {
             getITBPtr(tc)->invalidateMiscReg();
             getDTBPtr(tc)->invalidateMiscReg();
         }