Merge branch 'Alex/exit-system-call' into 'feature/system-calls'

Alex/exit system call

See merge request !12

.gitignore

@@ -10,3 +10,4 @@ examples/libc.a
 examples/my
 # Visual Studio folder
 /.vs
+/CppProperties.json

examples/Makefile

@@ -3,7 +3,7 @@ SRCDIR = ..
 # Test programs to compile, and a list of sources for each.
 # To add a new test, put its name on the PROGS list
 # and then add a name_SRC line that lists its source files.
-PROGS = cat cmp cp echo halt hex-dump ls mcat mcp mkdir pwd rm shell \
+PROGS = cat cmp cp echo exit halt hex-dump ls mcat mcp mkdir pwd rm shell \
 	bubsort insult lineup matmult recursor my touch
 
 # Should work from project 2 onward.
@@ -11,6 +11,7 @@ cat_SRC = cat.c
 cmp_SRC = cmp.c
 cp_SRC = cp.c
 echo_SRC = echo.c
+exit_SRC = exit.c
 halt_SRC = halt.c
 hex-dump_SRC = hex-dump.c
 insult_SRC = insult.c

examples/exit.c

+/* exit.c
+
+   Simple program to test whether running a user program works.
+ 	
+   Invokes the exit syscall to test if it works */
+
+#include <syscall.h>
+
+int
+main (void)
+{
+  exit (5);
+  /* not reached */
+}

userprog/syscall.c

@@ -72,7 +72,7 @@ syscall_handler (struct intr_frame *f UNUSED)
     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
-  thread_exit ();
 }

userprog/syscall_exit.c

+/*
+ * Terminates the current user program, returning status to the kernel. If the
+ * Process’s parent waits for it (see below), this is the status that will be
+ * Returned. Conventionally, a status of 0 indicates success and nonzero values
+ * Indicate errors.
+ *
+ * Authored by Alex Stratford
+ */
+
 #include "system_calls.h"
-#include "threads/interrupt.h"
+#include "threads/interrupt.h" // Dependency for intr_frame struct
+#include "threads/thread.h" // Dependency for thread struct
 
 void syscall_exit(struct intr_frame *f) {
-  (void*)0;
+	struct thread *current_thread = thread_current(); // Sets current thread
+	// pop off first int argument from interrupt frame
+	int exit_code = *((int*)f->esp + 1);
+	current_thread->exit_code = exit_code; // Returns exit code to kernel
+	thread_exit(); // Exiting current thread
 }
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