adds non-vectored interrupt handler

env/ehrenberg/init.c

@@ -92,12 +92,18 @@ void __attribute__((weak)) default_handler(void) {
   puts("default handler\n");
 }
 
+void __attribute__((weak)) interrupt_handler(unsigned) {
+  puts("interrupt handler\n");
+}
+
 uint32_t handle_trap(uint32_t mcause, uint32_t mepc, uint32_t sp){
   if ((mcause & MCAUSE_INT) && ((mcause & MCAUSE_CAUSE) == IRQ_M_EXT)) {
     handle_m_ext_interrupt();
     // External Machine-Level interrupt from PLIC
   } else if ((mcause & MCAUSE_INT) && ((mcause & MCAUSE_CAUSE) == IRQ_M_TIMER)){
     handle_m_time_interrupt();
+  } else if(!(mcause&MCAUSE_INT)) {
+    interrupt_handler(mcause& ~MCAUSE_INT);
   } else {
     write(1, "trap\n", 5);
     _exit(1 + mcause);

env/tgc_vp

@@ -1 +1 @@
-ehrenberg/
+ehrenberg