add lab answers

labcodes_answer/lab7_result/user/libs/panic.c

@@ -0,0 +1,28 @@
+#include <defs.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <ulib.h>
+#include <error.h>
+
+void
+__panic(const char *file, int line, const char *fmt, ...) {
+    // print the 'message'
+    va_list ap;
+    va_start(ap, fmt);
+    cprintf("user panic at %s:%d:\n    ", file, line);
+    vcprintf(fmt, ap);
+    cprintf("\n");
+    va_end(ap);
+    exit(-E_PANIC);
+}
+
+void
+__warn(const char *file, int line, const char *fmt, ...) {
+    va_list ap;
+    va_start(ap, fmt);
+    cprintf("user warning at %s:%d:\n    ", file, line);
+    vcprintf(fmt, ap);
+    cprintf("\n");
+    va_end(ap);
+}
+