Re: sysdeps/unix/sysv/linux directory structure question

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 03/11/2016 16:12, Steve Ellcey wrote:
> On Thu, 2016-11-03 at 18:01 +0000, Joseph Myers wrote:
>> On Thu, 3 Nov 2016, Steve Ellcey wrote:
>>
>>>
>>> So I have several questions.  What is the difference between
>>> sysdeps/unix/sysv/linux and sysdeps/unix/sysv/linux/generic and why
>>> are some files in one vs. the other vs. both?   Is generic only for
>>> 64-
>> generic is for newer architectures using the generic syscall ABI,
>> where 
>> syscalls that can be implemented in terms of newer syscalls are
>> generally 
>> omitted (so only statat syscalls not the older stat ones, for
>> example), 
>> and where structures are the same between different architectures as
>> far 
>> as possible (whereas various structures on older architectures
>> commonly 
>> tried to follow the layout used by some proprietary Unix on that 
>> architecture).
>>
>>>
>>> bit kernels?  Is that why it has a wordsize-32 subdirectory?  Are
>> The generic syscall ABI only has 64-bit versions of various
>> structures, 
>> with 32-bit architectures expected to do EOVERFLOW handling in
>> userspace.
> 
> So this use of 'generic' is different than the 'sysdeps/generic'
> directory.  I.e. sysdeps/generics is automatically added to the end of
> the sysdep directory search list, but 'sysdeps/unix/sysv/linux/generic'
> is only going to be used if it appears in a targets Implies file.  Is
> that correct?

Yes, my understanding is 'sysdeps/generics' is glibc defined internal 
semantics, where the linux/generic means the kernel abi (recall that
glibc still supports non-linux targets).