[sparc64] kernel OOPS with gcc 7.1 / 7.2

[David Miller]

From: Anthony Yznaga <anthony.yznaga at oracle.com>
Date: Tue, 15 Aug 2017 17:45:12 -0700

> I compiled a kernel with gcc 7 and found that the compiler inserted a
> call to __multi3() in mq_attr_ok().  The sparc64 implementation of
> __multi3() was added by 1b4af13ff2cc specifically for gcc 7 and later,
> but it clobbers %g4 and %g5.  Not sure if that was intended but it
> looks like __multi3() is not safe to call from kernel code.

Good catch, we have to redo the register allocation in that routine
to fix this.