arch-arm: ELUsingAArch32K from armarm pseudocode

This patch implements the ELUsingAArch32K pseudocode, which is returning
true if the provided Exception Level is using A32 ISA, but it is not
panicking (quitting simulation) if the information is unknown (see
documentation).
The panicking is the current behaviour of the ELIs32 utility in gem5.

Change-Id: Iad7b56077d7e0f8ee223b5b9593cb8097f26bb29
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/7222
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/src/arch/arm/utility.hh b/src/arch/arm/utility.hh
index 6e4e76b75..8efe4ad10 100644
--- a/src/arch/arm/utility.hh
+++ b/src/arch/arm/utility.hh
@@ -157,6 +157,24 @@ currEL(ThreadContext *tc)
     return (ExceptionLevel) (uint8_t) cpsr.el;
 }
 
+/**
+ * This function checks whether selected EL provided as an argument
+ * is using the AArch32 ISA. This information might be unavailable
+ * at the current EL status: it hence returns a pair of boolean values:
+ * a first boolean, true if information is available (known),
+ * and a second one, true if EL is using AArch32, false for AArch64.
+ *
+ * @param tc The thread context.
+ * @param el The target exception level.
+ * @retval known is FALSE for EL0 if the current Exception level
+ *               is not EL0 and EL1 is using AArch64, since it cannot
+ *               determine the state of EL0; TRUE otherwise.
+ * @retval aarch32 is TRUE if the specified Exception level is using AArch32;
+ *                 FALSE otherwise.
+ */
+std::pair<bool, bool>
+ELUsingAArch32K(ThreadContext *tc, ExceptionLevel el);
+
 bool ELIs32(ThreadContext *tc, ExceptionLevel el);
 
 bool ELIs64(ThreadContext *tc, ExceptionLevel el);