[PATCH v4 1/2] y2038: linux: Provide __timerfd_gettime64 implementation

[Adhemerval Zanella]

On 07/01/2020 11:25, Lukasz Majewski wrote:
> Hi Adhemerval,
> 
>> On 07/01/2020 06:27, Lukasz Majewski wrote:
>>
>>>> As a side note, now that arch-syscall patch is upstream should we
>>>> assume that for !__ASSUME_TIME64_SYSCALLS the
>>>> __NR_timerfd_gettime64 should be defined (meaning that Linux
>>>> supports time64 for all 32-bit architectures)?  
>>>
>>> Only Linux version >= 5.1 supports 64 bit time on archs with
>>> __WORDSIZE = 32. I do guess (but I may be wrong here) that the
>>> arch-syscall is supposed to reflect the exact syscalls provided by
>>> kernel headers used for building (to help with validation of Y2038
>>> patches).  
>>
>> The arch-syscall is now autogenerated from the latest kernel release
>> defined in build-many-glibcs.py. So the question is whether Linux
>> support and enforces time64 support on all and future 32-bit 
>> architectures or if there is still some missing ones (as it has
>> happen on some syscall additions, where some architecture lag
>> behind some releases).
> 
> This question would be best answered by Arnd (CC'ed) IMHO. From what I
> know all 32 bit architectures gained syscalls covered by
> __ASSUME_TIME64_SYSCALLS from Linux 5.1+.
> 
> The arch-syscall seems to me like a mean to test for example the time
> related syscalls which use different versions (32bit time vs 64 bit) on
> different archs. Notable example - clock_gettime(). Am I right?

The arch-syscall is a way to decouple the build from the kernel header
used on build, which might simplify the logic to use some kernel 
features.

On the clock_gettime, for instance, as Arnd has indicated we can
assume that __NR_clock_gettime64 will be always presented for
!__ASSUME_TIME64_SYSCALLS.

It would be interesting if kernel also could enforce that new
generic syscalls would be wire-up, or at least the syscall number
reserved; once a new generic syscall is introduced.  It would
simplify the __ASSUME_* macro, not requiring the arch-specific
overrides on some architectures.

> 
> The __clock_gettime64 is going to be exported (as clock_gettime
> redirection) on 32 bit archs which are going to be Y2038 safe (with 64
> bit time_t).
> 
>> clock_gettime64 would be suffice (with a {weak,strong}_alias).
>>
> 
> The internal in-glibc usage (calling) of clock_gettime() shall be
> replaced by either __clock_gettime64 or clock_gettime64. I would prefer
> the former as it reflects that it is internal function (with __ prefix).

It required to be the former because we also need to take in consideration
linking namespace pollution. 

> 
>> However I do think we should fix it to avoid such confusion why there 
>> is a hidden_proto and not a hidden_def.
> 
> +1.

Ack, I will send a patch.