Re: Update kernel-features.h files for Linux 5.1

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

On 10/05/2019 12:07, Adhemerval Zanella wrote:
> 
> 
> On 10/05/2019 07:27, Stepan Golosunov wrote:
>> 09.05.2019 в 23:00:37 +0000 Joseph Myers написал:
>>> Linux 5.1 adds missing syscalls to the syscall table for many Linux
>>> kernel architectures.  This patch updates the kernel-features.h
>>> headers accordingly.  I believe the statfs64 structure used by alpha
>>> matches what the new kernel syscalls use, but that should be reviewed
>>> carefully.
>>>
>>> Tested with build-many-glibcs.py.
>>
>> The newly added direct ipc syscalls are different from the old ones:
>>
>> 1. They do not accept IPC_64.  This means that __IPC_64 should be set
>> to zero when new syscalls are used.  And new syscalls can not be used
>> for compat functions like __old_semctl.
> 
> So it seems we will need to conditionally set __IPC_64 based on kernel
> version. It also seems that our default value on generic ipc_priv.h
> is not really expressing the kernel ABI.
> 
>>
>> (Hmm.  Is __old_msgctl already buggy due to its use of __IPC_64 when
>> __ASSUME_DIRECT_SYSVIPC_SYSCALLS is defined?  Is there any
>> architecture with both __ASSUME_DIRECT_SYSVIPC_SYSCALLS and
>> __old_msgctl currently?)
> 
> The architectures that exports msgctl@GLIBC_2.0 as compat symbol are
> alpha, i686, m68k, mips-o32, powerpc32, s390-32, and sparc32. And
> from these one alpha currently is the only architecture that defines
> __ASSUME_DIRECT_SYSVIPC_SYSCALLS. So it is buggy for alpha currently
> and it would be for the aforementioned architectures once they
> start to use wire-up syscall.
> 
> 
>>
>> 2. semtimedop does not exist on 32-bit ABIs.  They have
>> semtimedop_time64 instead.
>> (I also think that ipc with IPCOP_semtimedop was accidentally made to
>> behave like semtimedop_time64 in 32-bit builds of linux 5.1.  But that
>> would be a kernel bug.)
> 
> So it seems we would need to either add an __ASSUME specific for semtimedop
> to just enable wire-up calls if time64 is defined or add another pre-processor
> check to see if __NR_semtimeop is defined as well.
> 
> 
> To summarize, I think we need too:
> 
> 1. Fix Linux msgctl compat function to remove __IPC64.
> 
> 2. Move __IPC64 to kernel-feature.h and define it based on kernel version
>    along with __ASSUME_DIRECT_SYSVIPC_SYSCALLS.
> 
> 3. Only use wire-up semtimeop iff __NR_semtimedop is also defined.
> 

It seems semop would also need be handled this way.