linux-kernel - Re: [PATCH v2 3/4] kstrtox: add unit tests for memparse

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Date: Wed, 3 Jan 2024 07:25:33 +1030
From: Qu Wenruo <quwenruo.btrfs@....com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>, Qu Wenruo <wqu@...e.com>
Cc: linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
 akpm@...ux-foundation.org, christophe.jaillet@...adoo.fr,
 andriy.shevchenko@...ux.intel.com, David.Laight@...lab.com, ddiss@...e.de
Subject: Re: [PATCH v2 3/4] kstrtox: add unit tests for memparse_safe()



On 2024/1/2 23:53, Geert Uytterhoeven wrote:
> Hi Qu,
>
> On Tue, Jan 2, 2024 at 5:13 AM Qu Wenruo <wqu@...e.com> wrote:
>> The new tests cases for memparse_safe() include:
>>
>> - The existing test cases for kstrtoull()
>>    Including all the 3 bases (8, 10, 16), and all the ok and failure
>>    cases.
>>    Although there are something we need to verify specific for
>>    memparse_safe():
>>
>>    * @retptr and @value are not modified for failure cases
>>
>>    * return value are correct for failure cases
>>
>>    * @retptr is correct for the good cases
>>
>> - New test cases
>>    Not only testing the result value, but also the @retptr, including:
>>
>>    * good cases with extra tailing chars, but without valid prefix
>>      The @retptr should point to the first char after a valid string.
>>      3 cases for all the 3 bases.
>>
>>    * good cases with extra tailing chars, with valid prefix
>>      5 cases for all the suffixes.
>>
>>    * bad cases without any number but stray suffix
>>      Should be rejected with -EINVAL
>>
>> Signed-off-by: Qu Wenruo <wqu@...e.com>
>
> Thanks for your patch!
>
>> --- a/lib/test-kstrtox.c
>> +++ b/lib/test-kstrtox.c
>> @@ -268,6 +268,237 @@ static void __init test_kstrtoll_ok(void)
>>          TEST_OK(kstrtoll, long long, "%lld", test_ll_ok);
>>   }
>>
>> +/*
>> + * The special pattern to make sure the result is not modified for error cases.
>> + */
>> +#define ULL_PATTERN            (0xefefefef7a7a7a7aULL)
>> +#if BITS_PER_LONG == 32
>> +#define POINTER_PATTERN                (0xefef7a7a7aUL)
>
> This pattern needs 40 bits to fit, so it doesn't fit in a 32-bit
> unsigned long or pointer.  Probably you wanted to use 0xef7a7a7aUL
> instead?

My bad, one extra byte...

>
>> +#else
>> +#define POINTER_PATTERN                (ULL_PATTERN)
>> +#endif
>
> Shouldn't a simple cast to uintptr_t work fine for both 32-bit and
> 64-bit systems:
>
>      #define POINTER_PATTERN  ((uintptr_t)ULL_PATTERN)
>
> Or even better, incorporate the cast to a pointer:
>
>      #define POINTER_PATTERN  ((void *)(uintptr_t)ULL_PATTERN)

The problem is reported by sparse, which warns about that ULL_PATTERN
converted to a pointer would lose its width:

lib/test-kstrtox.c:339:40: sparse: sparse: cast truncates bits from
constant value (efefefef7a7a7a7a becomes 7a7a7a7a)

I'm not sure if using uiintptr_t would solve it, thus I go the macro to
switch the value to avoid the static checker's warning.

I tried to check how other locations handles patterned pointer value,
like CONFIG_INIT_STACK_ALL_PATTERN, but they're either relying on the
compiler or just memset().

Any better idea to solve the problem in a better way?

Thanks,
Qu

>
> so you can drop the extra cast when assigning/comparing retptr below.
>
>> +
>> +/* Want to include "E" suffix for full coverage. */
>> +#define MEMPARSE_TEST_SUFFIX   (MEMPARSE_SUFFIX_K | MEMPARSE_SUFFIX_M |\
>> +                                MEMPARSE_SUFFIX_G | MEMPARSE_SUFFIX_T |\
>> +                                MEMPARSE_SUFFIX_P | MEMPARSE_SUFFIX_E)
>> +
>> +static void __init test_memparse_safe_fail(void)
>> +{
>
> [...]
>
>> +       for_each_test(i, tests) {
>> +               const struct memparse_test_fail *t = &tests[i];
>> +               unsigned long long tmp = ULL_PATTERN;
>> +               char *retptr = (char *)POINTER_PATTERN;
>> +               int ret;
>
> [...]
>
> +               if (retptr != (char *)POINTER_PATTERN)
>
> Gr{oetje,eeting}s,
>
>                          Geert
>