[PATCH] Linux: Support __IPC_64 in sysvctl *ctl command arguments

[Florian Weimer]

* Florian Weimer via Libc-alpha:

> Old applications pass __IPC_64 as part of the command argument because
> old glibc did not check for unknown commands, and passed through the
> arguments directly to the kernel, without adding __IPC_64.
> Applications need to continue doing that for old glibc compatibility,
> so this commit enables this approach in current glibc.
>
> For msgctl and shmctl, if no translation is required, make
> direct system calls, as we did before the time64 changes.  If
> translation is required, mask __IPC_64 from the command argument.
>
> For semctl, the union-in-vararg argument handling means that
> translation is needed on all architectures.
>
> Tested on i686-linux-gnu, powerpc64le-linux-gnu, x86_64-linux-gnu.
> Built with build-many-glibcs.py.

I've filed a bug:

  Restore IPC_64 support in sysvipc *ctl functions
  <https://sourceware.org/bugzilla/show_bug.cgi?id=29771>

I'm going to reference it in the commit message.

Thanks,
Florian