arch-arm: generic method for getting an ArmSystem

This patch provides a generic method for casting a System object
into an ArmSystem object. This is specially useful in dev-arm,
since devices by default obtain a generic System reference which
needs to be casted to use ArmSystem-specific functionality.

Change-Id: Ib100002413cb48cd93772dcf38f13be65badd1d3
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/22426
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/arch/arm/system.cc

@@ -174,6 +174,14 @@ ArmSystem::initState()
     }
 }
 
+ArmSystem *
+ArmSystem::getArmSystem(System *sys)
+{
+    ArmSystem *a_sys = dynamic_cast<ArmSystem *>(sys);
+    assert(a_sys);
+    return a_sys;
+}
+
 ArmSystem*
 ArmSystem::getArmSystem(ThreadContext *tc)
 {

src/arch/arm/system.hh

@@ -284,6 +284,13 @@ class ArmSystem : public System
     /** Is Arm Semihosting support enabled? */
     bool haveSemihosting() const { return semihosting != nullptr; }
 
+    /**
+     * Casts the provided System object into a valid ArmSystem, it fails
+     * otherwise.
+     * @param sys System object to cast
+     */
+    static ArmSystem *getArmSystem(System *sys);
+
     /**
      * Returns a valid ArmSystem pointer if using ARM ISA, it fails
      * otherwise.