Add page tests to string/test-strnlen.

May be tricky for otimized implementations to handle strings around
page boundary once, for instance, it is performed unaligned loads or
when maxlen is used as a hint for vectorized loops. The test cases
should unveil regression bugs on these cases.

To some extend do_random_tests in string/test-strnlen tests strings
placed at page end but it does not cover all cases. So this change
adds tests which consists of placing strings of varying sizes ending
at the page boundary. It also combines with different values of maxlen.

Tested on ppc64le and x86_64.

	* string/test-strnlen.c (do_page_tests): New function
	to check length of strings ending at the page boundary.
	(test_main): Added call to the do_page_tests function.

2 files changed, 60 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 7ee1347f40..43cb215fe6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,10 @@
 2017-04-05  Wainer dos Santos Moschetta  <wainersm@linux.vnet.ibm.com>
+
+	* string/test-strnlen.c (do_page_tests): New function
+	to check length of strings ending at the page boundary.
+	(test_main): Added call to the do_page_tests function.
+
+2017-04-05  Wainer dos Santos Moschetta  <wainersm@linux.vnet.ibm.com>
 	    Paul E. Murphy  <murphyp@linux.vnet.ibm.com>
 
 	* sysdeps/powerpc/powerpc64/multiarch/Makefile
diff --git a/string/test-strnlen.c b/string/test-strnlen.c
index 277146fb6c..e56cdb6708 100644
--- a/string/test-strnlen.c
+++ b/string/test-strnlen.c
@@ -143,6 +143,59 @@ do_random_tests (void)
     }
 }
 
+/* Tests meant to unveil fail on implementation that does not access bytes
+   around the page boundary accordingly.  */
+static void
+do_page_tests (void)
+{
+  size_t i, exp_len, start_offset, offset;
+  /* Calculate the null character offset.  */
+  size_t last_offset = (page_size / sizeof (CHAR)) - 1;
+
+  CHAR *s = (CHAR *) buf2;
+  memset (s, 65, (last_offset - 1));
+  s[last_offset] = 0;
+
+  /* Place short strings ending at page boundary.  */
+  offset = last_offset;
+  for (i = 0; i < 128; i++)
+    {
+      /* Decrease offset to stress several sizes and alignments.  */
+      offset--;
+      exp_len = last_offset - offset;
+      FOR_EACH_IMPL (impl, 0)
+        {
+          /* Varies maxlen value to cover the cases where it is:
+               - larger than length;
+               - slightly greater than length;
+               - equal to length;
+               - slightly less than length.  */
+          do_one_test (impl, (CHAR *) (s + offset), page_size, exp_len);
+          do_one_test (impl, (CHAR *) (s + offset), exp_len + 1, exp_len);
+          do_one_test (impl, (CHAR *) (s + offset), exp_len, exp_len);
+          if (exp_len > 0)
+            do_one_test (impl, (CHAR *) (s + offset), exp_len - 1, exp_len - 1);
+        }
+    }
+
+  /* Place long strings ending at page boundary.  */
+  start_offset = (last_offset + 1) / 2;
+  for (i = 0; i < 64; ++i)
+    {
+      /* Increase offset to stress several alignments.  */
+      offset = start_offset + i;
+      if (offset >= (last_offset + 1))
+        break;
+      exp_len = last_offset - offset;
+      FOR_EACH_IMPL (impl, 0)
+        {
+          /* Checks only for maxlen much larger than length because smaller
+             values are already covered in do_random_tests function.  */
+          do_one_test (impl, (CHAR *) (s + offset), page_size, exp_len);
+        }
+    }
+}
+
 int
 test_main (void)
 {
@@ -188,6 +241,7 @@ test_main (void)
     }
 
   do_random_tests ();
+  do_page_tests ();
   return ret;
 }