TD3:II.1 First working version of ForkExec

But need to implement Process exit...

code/userprog/userthread.cc

@@ -88,8 +88,46 @@ void do_ThreadExit(){
     if ( currentThread->space->threads == 0 ){
         // No threads remains, desallocate addrspace
         delete currentThread->space;
-        Exit(0);
+        currentThread->space = NULL;
     }
     currentThread->Finish();
 }
+
+void StartUserProc( void * args ){
+    currentThread->space->InitRegisters();
+    currentThread->space->RestoreState(); 
+    machine->DumpMem("memory.svg");
+    machine->Run();
+}
+
+int do_ForkExec( const char * c){
+    DEBUG('x', "Enter ForkExec\n");
+    AddrSpace * space;
+	Thread * fork;
+	OpenFile * file;            
+
+	file = fileSystem->Open(c);
+
+	if (file == NULL) {
+		printf("Unable to open file %s\n", file);	
+		return -1;
+	}
+		
+    try { 
+    	space = new AddrSpace(file);
+    }catch(const std::bad_alloc& e) {
+    	printf("==> BAD ALLOC ERROR: no empty space\n");
+    	delete space;
+    	ASSERT(false);
+    }
+    
+	fork = new Thread("forkThread");	
+	fork->space = space;
+	fork->Start(StartUserProc, NULL);
+
+	delete file;
+
+	return 0;
+}
+
 #endif