1 files changed, 24 insertions, 0 deletions
diff --git a/usertests.c b/usertests.c
index 2bd21ba..247cc95 100644
--- a/usertests.c
+++ b/usertests.c
@@ -1261,6 +1261,29 @@ sbrktest(void)
   printf(stdout, "sbrk test OK\n");
 }
 
+void
+stacktest(void)
+{
+  printf(stdout, "stack test\n");
+  char dummy = 1;
+  char *p = &dummy;
+  int ppid = getpid();
+  int pid = fork();
+  if(pid < 0){
+    printf(stdout, "fork failed\n");
+    exit();
+  }
+  if(pid == 0){
+    // should cause a trap:
+    p[-4096] = 'z';
+    kill(ppid);
+    printf(stdout, "stack test failed: page before stack was writeable\n");
+    exit();
+  }
+  wait();
+  printf(stdout, "stack test OK\n");
+}
+
 int
 main(int argc, char *argv[])
 {
@@ -1272,6 +1295,7 @@ main(int argc, char *argv[])
   }
   close(open("usertests.ran", O_CREATE));
 
+  stacktest();
   sbrktest();
 
   opentest();