r passed
to the system call is extended to 64 bit, but the high order bits are not
set to zero. The kernel detects the invalid user space pointer and
returns -EFAULT. To solve the problem, sys32_sigaltstack_wrapper()
instead of sys32_sigaltstack() has to be called. The wrapper function sets
the high order bits to zero.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>