added external_sim_device_t class and methods

riscv/devices.cc

@@ -155,3 +155,25 @@ void mem_t::dump(std::ostream& o) {
     }
   }
 }
+
+external_sim_device_t::external_sim_device_t(void* sim) 
+  : external_simulator(sim) {}
+
+void external_sim_device_t::set_simulator(void* sim) {
+  external_simulator = sim;
+}
+
+bool external_sim_device_t::load(reg_t addr, size_t len, uint8_t* bytes) {
+  if (unlikely(external_simulator == nullptr)) return false;
+  return static_cast<abstract_sim_if_t*>(external_simulator)->do_load(addr, len, bytes);
+}
+
+bool external_sim_device_t::store(reg_t addr, size_t len, const uint8_t* bytes) {
+  if (unlikely(external_simulator == nullptr)) return false;
+  return static_cast<abstract_sim_if_t*>(external_simulator)->do_store(addr, len, bytes);
+}
+
+reg_t external_sim_device_t::size() {
+  if (unlikely(external_simulator == nullptr)) return 0;
+  return PGSIZE; // TODO: proper size
+}

riscv/devices.h

@@ -78,6 +78,18 @@ public:
   virtual bool do_store(reg_t addr, size_t len, const uint8_t* bytes) = 0;
 };
 
+class external_sim_device_t : public abstract_device_t {
+public:
+  external_sim_device_t(void* sim);
+  void set_simulator(void* sim);
+  bool load(reg_t addr, size_t len, uint8_t* bytes) override;
+  bool store(reg_t addr, size_t len, const uint8_t* bytes) override;
+  reg_t size() override;
+
+private:
+  void* external_simulator;
+};
+
 class clint_t : public abstract_device_t {
  public:
   clint_t(const simif_t*, uint64_t freq_hz, bool real_time);