Multiple cleanups and improvements

- Cleanup exception trigger code
- Cleanup division to divide by 0
- Cleanup SRET code
- Cleanup CSR code
- Added interrupts
- Added TIMER interrupt

src/main.c

@@ -2,6 +2,7 @@
 #include "memory/memory.h"
 #include "bootloader/bootloader.h"
 #include "cpu/rv32cpu.h"
+#include "cpu/interrupt.h"
 #include "gdbstub/gdbstub.h"
 #include "devices/uart/uart.h"
 
@@ -31,34 +32,20 @@ int main(int argc, char** argv)
 		gdbstub_wait_for_connection();
 	}
 
+	// Initialize timer for timer interrupt
+	interrupt_timer_setup();
+
 	// CPU simulation : create cpu0 thread
 	if(!gdbstub) cpu0->sim_ticks_left = -1; // Simulate forever
 	pthread_t cpu0_thread;
 	pthread_create(&cpu0_thread, 0, (void*) cpu_loop, cpu0);
 
-	// Wait for the simulation to end
+	// Wait forever, until simulation end (which should be an ecall shutdown)
+	pthread_join(cpu0_thread, 0);
 	if(gdbstub)
 	{
-		pthread_join(cpu0_thread, 0);
 		gdbstub_stop();
 	}
-	else
-	{
-		while(1)
-		{
-			pthread_mutex_lock(&cpu0_mutex);
-			pthread_cond_wait(&cpu0->sim_condition, &cpu0_mutex);
-			if(!cpu0->sim_ticks_left && cpu0->sim_ticks_done > 0)
-			{
-				// Simulation ended
-                break;
-			}
-			pthread_mutex_unlock(&cpu0_mutex);
-		}
-
-        fprintf(stderr, "Simulation ended (in a non-debug environment)\n");
-        return cpu0->regs.a0;
-	}
 
 	return 0;
 }