[PATCH v6] string: Adds tests for test-strncasecmp and test-strncpy

[Raphael M Zinsly]

On 10/07/2020 10:56, Lucas A. M. Magalhaes wrote:
> Hi Raphael,
> Thanks fo the patch.
> 
> Quoting Raphael Moreira Zinsly (2020-07-08 17:20:09)
>> Changes since v5:
>> string/test-strncpy.c:
>>          - Adjusted s1 and s2 placements.
>>          - Used the same pattern as test-strncasecmp.
>>
>> --- >8 ---
>>
>> Adds tests to check if strings placed at page bondaries are
>> handled correctly by strncasecmp and strncpy similar to tests
>> for strncmp and strnlen.
>> ---
>>   string/test-strncasecmp.c | 44 +++++++++++++++++++++++++++++++++++++++
>>   string/test-strncpy.c     | 36 ++++++++++++++++++++++++++++++++
>>   2 files changed, 80 insertions(+)
>>
>> diff --git a/string/test-strncasecmp.c b/string/test-strncasecmp.c
>> index 6a9c27beae..628135b962 100644
>> --- a/string/test-strncasecmp.c
>> +++ b/string/test-strncasecmp.c
>> @@ -137,6 +137,49 @@ 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)
>> +{
>> +  char *s1, *s2;
>> +  int exp_result;
>> +  /* Assumes up to 512-bit wide read/stores.  */
>> +  const size_t maxoffset = 64;
>> +
>> +  s1 = (char *) buf1 + (BUF1PAGES) * page_size - maxoffset;
>> +  memset (s1, 'a', maxoffset - 1);
>> +  s1[maxoffset - 1] = '\0';
> 
> OK.
>> +
>> +  s2 = (char *) buf2 + page_size - maxoffset;
>> +  memset (s2, 'a', maxoffset - 1);
>> +  s2[maxoffset - 1] = '\0';
>> +
> OK. buf2 is only 1 page size.
> 
>> +  /* At this point s1 and s2 points to distinct memory regions containing
>> +     "aa..." with size of 63 plus '\0'.  Also, both strings are bounded to a
>> +     page with write/read 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 checks for all possible offset up to maxoffset for both
>> +     inputs with a size larger than the string (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++)
>> +       {
>> +         exp_result = off1 == off2
>> +                       ? 0
>> +                       : off1 < off2
>> +                         ? 'a'
>> +                         : -'a';
>> +
>> +         FOR_EACH_IMPL (impl, 0)
>> +           check_result (impl, s1 + off1, s2 + off2, maxoffset + 1,
>> +                         exp_result);
>> +       }
>> +    }
>> +}
>> +
> 
> OK.
>>   static void
>>   do_random_tests (void)
>>   {
>> @@ -334,6 +377,7 @@ test_locale (const char *locale)
>>       }
>>   
>>     do_random_tests ();
>> +  do_page_tests ();
>>   }
>>   
> 
> OK.
>>   int
>> diff --git a/string/test-strncpy.c b/string/test-strncpy.c
>> index c978753ad8..c8d4ad58a6 100644
>> --- a/string/test-strncpy.c
>> +++ b/string/test-strncpy.c
>> @@ -155,6 +155,41 @@ 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;
>> +  /* Assumes up to 512-bit wide read/stores.  */
>> +  const size_t maxoffset = 64;
>> +
>> +  /* Put s1 at the edge of buf1's last page.  */
>> +  s1 = (CHAR *) buf1 + (BUF1PAGES) * (page_size / sizeof(CHAR)) - maxoffset;
>> +  /* Put s2 almost at the edge of buf2, it needs room to put a string with
>> +     size of maxoffset + 1 at s2 + maxoffset.  */
>> +  s2 = (CHAR *) buf2 + (page_size / sizeof(CHAR)) - (maxoffset + 1) * 2;
>> +
> 
> IDK if was the intention. If you add maxoffset to s2 it will still leave
> maxoffset + 2 bytes for s2 and not maxoffset as the comment says.
> 
That's right, leaving the + 1 was a mistake. Thanks for catching it!

>> +  MEMSET (s1, 'a', maxoffset - 1);
>> +  s1[maxoffset - 1] = '\0';
>> +
> 
> OK.
> 
>> +  /* Both strings are bounded to a page with write/read 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 offset 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);
> 
> maxoffset + 2?
>> +       }
>> +    }
>> +}
>> +
>>   static void
>>   do_random_tests (void)
>>   {
>> @@ -317,6 +352,7 @@ test_main (void)
>>       }
>>   
>>     do_random_tests ();
>> +  do_page_tests ();
>>     return ret;
>>   }
>>   
> 
> OK.
>> -- 
>> 2.26.2
>>

Best Regards,
-- 
Raphael Moreira Zinsly
IBM
Linux on Power Toolchain