adds initial semihosting host capabilities

src/iss/semihosting/semihosting.cpp

@@ -0,0 +1,22 @@
+#include "semihosting.h"
+#include <exception>
+#include <iss/vm_types.h>
+#include <stdexcept>
+template <typename T> void semihosting_callback(iss::arch_if* arch_if_ptr, T a0, T a1) {
+    if(a0 == 0x04 /*WRITE0*/) {
+        uint8_t character;
+        while(1) {
+            auto res = arch_if_ptr->read(iss::address_type::PHYSICAL, iss::access_type::DEBUG_READ, 0, a1, 1, &character);
+            if(res != iss::Ok)
+                return;
+            if(character == 0)
+                break;
+            putchar(character);
+            a1++;
+        }
+    } else {
+        throw std::runtime_error("Not Implemented Error");
+    }
+}
+template void semihosting_callback<uint32_t>(iss::arch_if* arch_if_ptr, uint32_t a0, uint32_t a1);
+template void semihosting_callback<uint64_t>(iss::arch_if* arch_if_ptr, uint64_t a0, uint64_t a1);

src/iss/semihosting/semihosting.h

@@ -0,0 +1,6 @@
+#ifndef _SEMIHOSTING_H_
+#define _SEMIHOSTING_H_
+#include <iss/arch_if.h>
+template <typename T> void semihosting_callback(iss::arch_if* arch_if_ptr, T a0, T a1);
+
+#endif