TD3:II.1 First working version of ForkExec

But need to implement Process exit...

code/userprog/exception.cc

@@ -226,6 +226,14 @@ ExceptionHandler (ExceptionType which)
             do_ThreadExit();
             break;
           }
+        case SC_ForkExec:
+          {
+            int s = machine->ReadRegister(4);
+            char * command = new char[MAX_STRING_SIZE];
+            int size = copyStringFromMachine(s, command, MAX_STRING_SIZE);
+            do_ForkExec(command);
+            break;
+          }
         #endif
 		default:
 		  {

code/userprog/syscall.h

@@ -40,6 +40,7 @@
 #define SC_GetInt       16
 #define SC_ThreadCreate 17
 #define SC_ThreadExit   18
+#define SC_ForkExec     19
 #endif
 #ifdef IN_USER_MODE
 
@@ -148,6 +149,7 @@ void PutInt(int n);
 void GetInt( int * n);
 int ThreadCreate(void f(void * args), void * args);
 void ThreadExit(void);
+int ForkExec ( const char * s);
 
 #endif // CHANGED
 

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

code/userprog/userthread.h

@@ -11,4 +11,5 @@ typedef struct {
 
 extern int do_ThreadCreate(int f, int arg);
 extern void do_ThreadExit();
+extern int do_ForkExec( const char * s);
 #endif