CVE-2017-5753
CVE-2017-5715

To prevent the unused registers %r8-%r15, from being used speculatively,
we clear them upon syscall entrance for code hygiene in 32 bit compatible
mode.
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>
(backported from commit 85910f3f9cd728acce9ef34a6df4f8bf8714d006)
Signed-off-by: Andy Whitcroft <apw@canonical.com>