Add skeleton of new write system call

Makefile.build

@@ -67,6 +67,7 @@ userprog_SRC += userprog/syscall_exit.c
 userprog_SRC += userprog/syscall_halt.c
 userprog_SRC += userprog/syscall_wait.c
 userprog_SRC += userprog/syscall_create.c
+userprog_SRC += userprog/syscall_write.c
 
 # No virtual memory code yet.
 #vm_SRC = vm/file.c			# Some file.

userprog/syscall.c

@@ -70,9 +70,11 @@ syscall_handler (struct intr_frame *f UNUSED)
   case SYSCALL_CREATE:
     syscall_create(f);
     break;
+  case SYSCALL_WRITE:
+    syscall_write(f);
+    break;
   default:
     printf ("WARNING: Invalid Syscall (%d)\n", syscall_number);
     thread_exit ();
   }
-  // TODO: remove this call to exit as we don't want all syscalls to make the thread exit
 }

userprog/syscall_write.c

+/*
+ * The Write System Call
+ *
+ * Authored by Joshua Saxby
+ */
+#include "system_calls.h"
+#include "threads/interrupt.h"
+
+void syscall_write(struct intr_frame *f) {
+    // TODO: implement me!
+    (void*)0;
+}

userprog/system_calls.h

@@ -35,6 +35,13 @@ void syscall_wait(struct intr_frame *f);
  */
 void syscall_create(struct intr_frame *f);
 
+/*
+ * Writes size bytes from buffer to the open file fd.
+ * Returns the number of bytes actually written, which may be less than size if
+ * some bytes could not be written.
+ */
+void syscall_write(struct intr_frame *f);
+
 /*
  * NOTE: There are more system calls implemented by Pintos but we are not
  * implementing them because the assignment brief does not ask of it.