X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Ftests%2Fuserprog%2Fboundary.c;h=2e81df48e0beb5c75489e6bdb8c781c39b771213;hb=16c7d34d02045bc7e6165a13c549a7968e074d4b;hp=50f2618d3db62852a7368630e267eba22afeb27d;hpb=615bf3b3d2a8573ed6fb9ddc0055745e163ac999;p=pintos-anon

diff --git a/src/tests/userprog/boundary.c b/src/tests/userprog/boundary.c
index 50f2618..2e81df4 100644
--- a/src/tests/userprog/boundary.c
+++ b/src/tests/userprog/boundary.c
@@ -1,3 +1,7 @@
+/* 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>
@@ -27,3 +31,14 @@ copy_string_across_boundary (const char *src)
   return p;
 }
 
+/* Returns an address that is invalid, but the preceding bytes
+ * are all valid. Used to position information such that the
+ * first byte of the information is valid, but not all the
+ * information is valid. */
+void *
+get_bad_boundary (void)
+{
+  /* This code assumes that dst will be in the highest page
+   * allocated to the user process. */
+  return (void *) ROUND_UP ((uintptr_t) (dst + sizeof(dst) - 1), 4096);
+}