1 files changed, 33 insertions, 0 deletions
diff --git a/src/tests/userprog/boundary.c b/src/tests/userprog/boundary.c
new file mode 100644
index 0000000..59907ec
--- /dev/null
+++ b/src/tests/userprog/boundary.c
@@ -0,0 +1,33 @@
+/* Utility function for tests that try to break system calls by
+   passing them data that crosses from one virtual page to
+   another. */
+
+#include <inttypes.h>
+#include <round.h>
+#include <string.h>
+#include "tests/userprog/boundary.h"
+
+static char dst[8192];
+
+/* Returns the beginning of a page.  There are at least 2048
+   modifiable bytes on either side of the pointer returned. */
+void *
+get_boundary_area (void) 
+{
+  char *p = (char *) ROUND_UP ((uintptr_t) dst, 4096);
+  if (p - dst < 2048)
+    p += 4096;
+  return p;
+}
+
+/* Returns a copy of SRC split across the boundary between two
+   pages. */
+char *
+copy_string_across_boundary (const char *src) 
+{
+  char *p = get_boundary_area ();
+  p -= strlen (src) < 4096 ? strlen (src) / 2 : 4096;
+  strlcpy (p, src, 4096);
+  return p;
+}
+