Added basic SBI support

src/devices/sbi/sbi.c

@@ -0,0 +1,27 @@
+#include "sbi.h"
+
+#include <stdio.h>
+
+void sbi_call(rv32_cpu_t* cpu, uint32_t extension_id, uint32_t func_id)
+{
+	switch(extension_id)
+	{
+		case SBI_EXTENSION_LEGACY_CONSOLE_PUTCHAR:
+		{
+            printf("%c", cpu->regs.a0);
+            cpu->regs.a0 = 0;
+            break;
+		}
+        case SBI_EXTENSION_LEGACY_SHUTDOWN:
+        {
+			printf("sbi_call: shutdown, goodbye !\n");
+            cpu->sim_ticks_left = 1;
+            break;
+        }
+		default:
+		{
+			fprintf(stderr, "sbi_call: unknown extension id 0x%x\n", extension_id);
+            break;
+		}
+	}
+}

src/devices/sbi/sbi.h

@@ -0,0 +1,11 @@
+#ifndef SBI_H
+#define SBI_H
+
+#include "cpu/rv32cpu.h"
+
+#define SBI_EXTENSION_LEGACY_CONSOLE_PUTCHAR 0x1
+#define SBI_EXTENSION_LEGACY_SHUTDOWN 0x8
+
+void sbi_call(rv32_cpu_t* cpu, uint32_t extension_id, uint32_t func_id);
+
+#endif