[PATCH v8] string: Adds tests for test-strncasecmp and test-strncpy

[Paul E Murphy]

On 7/29/20 1:27 PM, Raphael Moreira Zinsly via Libc-alpha wrote:
> Changes since v7:
> 	- Fixed comments to make them clearer.
> 
> --- >8 ---
> 
> Adds tests to check if strings placed at page bondaries are

Minor grammar/spelling nit: "Add tests" and "page boundaries".

Similarly, commit title might be improved by rewording to something 
like: "string: test strncasecmp and strncpy near page boundaries"

> handled correctly by strncasecmp and strncpy similar to tests
> for strncmp and strnlen.
> ---
>   string/test-strncasecmp.c | 43 +++++++++++++++++++++++++++++++++++++++
>   string/test-strncpy.c     | 35 +++++++++++++++++++++++++++++++
>   2 files changed, 78 insertions(+)
> 
> diff --git a/string/test-strncasecmp.c b/string/test-strncasecmp.c
> index 6a9c27beae..502222ed1d 100644
> --- a/string/test-strncasecmp.c
> +++ b/string/test-strncasecmp.c
> @@ -137,6 +137,48 @@ do_test (size_t align1, size_t align2, size_t n, size_t len, int max_char,
>       do_one_test (impl, s1, s2, n, exp_result);
>   }
> 
> +static void
> +do_page_tests (void)

This test looks OK.

>   static void
>   do_random_tests (void)
>   {
> @@ -334,6 +376,7 @@ test_locale (const char *locale)
>       }
> 
>     do_random_tests ();
> +  do_page_tests ();
>   }
> 
>   int
> diff --git a/string/test-strncpy.c b/string/test-strncpy.c
> index c978753ad8..2919bbe181 100644
> --- a/string/test-strncpy.c
> +++ b/string/test-strncpy.c
> @@ -155,6 +155,40 @@ do_test (size_t align1, size_t align2, size_t len, size_t n, int max_char)
>       do_one_test (impl, s2, s1, len, n);
>   }
> 
> +static void
> +do_page_tests (void)
> +{
> +  CHAR *s1, *s2;
> +  const size_t maxoffset = 64;
> +
> +  /* Put s1 at the maxoffset from the edge of buf1's last page.  */
> +  s1 = (CHAR *) buf1 + BUF1PAGES * page_size / sizeof(CHAR) - maxoffset;
> +  /* s2 needs room to put a string with size of maxoffset + 1 at s2 +
> +     (maxoffset - 1).  */

Does this only test the interesting page boundary case of s2 when off2 
== (maxoffset-1)?  Should the n of do_one_test instead be maxoffset + 
(maxoffset - off2) to ensure each iteration straddles the guard page of 
s1 and s2?

> +  s2 = (CHAR *) buf2 + page_size / sizeof(CHAR) - maxoffset * 2;
> +
> +  MEMSET (s1, 'a', maxoffset - 1);
> +  s1[maxoffset - 1] = '\0';
> +
> +  /* Both strings are bounded to a page with read/write access and the next
> +     page is protected with PROT_NONE (meaning that any access outside of the
> +     page regions will trigger an invalid memory access).
> +
> +     The loop copies the string s1 for all possible offsets up to maxoffset
> +     for both inputs with a size larger than s1 (so memory access outside the
> +     expected memory regions might trigger invalid access).  */
> +
> +  for (size_t off1 = 0; off1 < maxoffset; off1++)
> +    {
> +      for (size_t off2 = 0; off2 < maxoffset; off2++)
> +	{
> +	  FOR_EACH_IMPL (impl, 0)
> +	    do_one_test (impl, (s2 + off2), (s1 + off1), maxoffset - off1 - 1,
> +			 maxoffset + 1);
> +	}
> +    }
> +}