[LTP] [PATCH] open_posix_testsuite/mmap24-2: Support mips

[Hongzhi, Song]

On 11/27/18 9:51 PM, Cyril Hrubis wrote:
> Hi!
> First of all sorry for the late reply.
>
>> Mips will return EINVAL instead of ENOMEM as expected
>> if MAP_FIXED is set and the range of [addr + len) exceeds
>> TASK_SIZE.
>>
>> Linux kernel code: arch/mips/mm/mmap.c
>> if (flags & MAP_FIXED) {
>>      /* Even MAP_FIXED mappings must reside within TASK_SIZE */
>>      if (TASK_SIZE - len < addr)
>>          return -EINVAL;
>>
>> The POSIX specification says:
>> "If MAP_FIXED is set, mmap() may return MAP_FAILED and set errno to
>> [EINVAL]."
>> [http://pubs.opengroup.org/onlinepubs/9699919799/functions/mmap.html]
>>
>> So I think the mips kernel remains POSIX compliant.
> There is a subtle difference between the ENOMEM and EINVAL error for
> MAP_FIXED though.
>
> If you look at POSIX specification terminology it says that 'shall'
> defines mandatory features while 'may' describes optional features.
>
> Which means that the MAP_FIXED returning ENOMEM for addresses above
> TASK_SIZE is mandatory since it's defined in the shall fail list. And
> that EINVAL is recomended to be used for other unsuitable address that
> fit into the process address space but are not suitable for a different
> reasons which could be mostly translated to hardware limits.
>
> To sum it up, as far as I can tell mips is not POSIX confirmant here and
> even if this is a very minor issue we shouldn't change the test here.
>

Sorry for my recent ping-emails, because I missed your reply.

I follow your final above conclusion.


--Hongzhi