[LTP] [PATCH] mmap18: fix when PTHREAD_STACK_MIN < PAGE_SIZE

[Alexey Kodanev]

Hi Cyril,
On 12.07.2021 16:47, Cyril Hrubis wrote:
> Hi!
>> PTHREAD_STACK_MIN can be less than the page size, to be more
>> precise 2048 on musl. This value is used in the test as an
>> offset for a new stack address with mmap() + MAP_FIXED flag.
>> Though it might not be aligned to the page size.
>>
>> This breaks the test with musl:
>>
>>   tst_test.c:1311: TINFO: Timeout per run is 0h 05m 00s
>>   mmap18.c:98: TBROK: mmap(0x7fe67e2ee800,2048,3,306,-1,0) failed: EINVAL (22)
>>   mmap18.c:169: TFAIL: Child: exited with 2
>>   [...]
>>
>> The fix is to align mapped_size arg to the page size.
>>
>> Signed-off-by: Alexey Kodanev <aleksei.kodanev@bell-sw.com>
>> ---
>>  testcases/kernel/syscalls/mmap/mmap18.c | 7 ++++---
>>  1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/testcases/kernel/syscalls/mmap/mmap18.c b/testcases/kernel/syscalls/mmap/mmap18.c
>> index dc2926454..b37b29890 100644
>> --- a/testcases/kernel/syscalls/mmap/mmap18.c
>> +++ b/testcases/kernel/syscalls/mmap/mmap18.c
>> @@ -200,11 +200,12 @@ static void grow_stack_fail(size_t stack_size, size_t mapped_size)
>>  
>>  static void run_test(void)
>>  {
>> -	size_t stack_size = 8 * PTHREAD_STACK_MIN;
>> +	size_t pthread_stack = LTP_ALIGN(PTHREAD_STACK_MIN, getpagesize());
>> +	size_t stack_size = 8 * pthread_stack;
> 
> Looking at the code we have to align both stack size and mapped size so
> this is correct. I guess that we can save a bit by aligning each of them
> independently since 8 * PTHREAD_STACK_MIN would in most cases be aligned
> allready.
> 
> 	size_t pthread_stack = LTP_ALIGN(PTHREAD_STACK_MIN, getpagesize());
> 	size_t stack_size = LTP_ALIGN(8 * PTHREAD_STACK_MIN, getpagesize());
> 
> Either way this looks good so:
> 
> Reviewed-by: Cyril Hrubis <chrubis@suse.cz>

Thanks for review!

Applied the original patch, it keeps the original proportion between
stack_size and mapped_size for both libc, also stack_size divided by
two after that for the mapped_size arg (though it doesn't really
matter with 8 * 2048):

> 
>> -	grow_stack_success(stack_size, PTHREAD_STACK_MIN);
>> +	grow_stack_success(stack_size, pthread_stack);
>>  	grow_stack_success(stack_size, stack_size/2);
>> -	grow_stack_fail(stack_size, PTHREAD_STACK_MIN);
>> +	grow_stack_fail(stack_size, pthread_stack);
>>  	grow_stack_fail(stack_size, stack_size/2);
>>  }