* Rich Felker <dalias@libc.org> [2019-08-20 15:12:21 -0400]:
> We already have the first two, under BSD||GNU. Note that non-exposure
> under plain POSIX is not a choice here; AT_* is (perhaps wrongly, by
> oversight) not in the reserved namespace for fcntl.h.
> 
> I'm not sure if GNU-only is better than BSD||GNU; my leaning is
> towards keeping the latter.

ok.

> I think this is okay for now, but now that Linux has unified syscall
> numbers for all future syscalls, I wonder if we should add a
> bits/syscall_common.h or something that defines all the common ones in
> terms of some base macro, so that we don't have O(nm) growth here.

yes that would be useful.

> As before, the _OLD/_NEW names aren't needed for userspace. Rather the
> definition of the unadorned macro has to be changed from the old value
> to the new one when the time64 switchover happens (missing from the
> RFC/POC i386 commit in the "final time64 switch-over patch series"
> thread -- this needs fixing). The _OLD versions are already defined
> privately in arch/*/syscall_arch.h for 32-bit archs since commit
> 2e554617e5a6a41bf3f6c6306c753cd53abf728c, so ioctl.c can use them for
> translation.

ok.

> Also, I don't think it matters whether the _IOR macro is used or not
> since the naive switchover will require per-arch ioctl bits for all
> 32-bit archs, but maybe we can come up with a way to share some of the
> bits stuff between them and prevent introduction of new redundancy.
> Thoughts?

i see.

v2:
- AT_STATX_* are moved under _BSD_SOURCE|_GNU_SOURCE
- time_t related ioctl patch is dropped