In the default case, we don't need to use the stack, we can save r7 with
ip register (that what does eglibc).
This allow to fix vfork data corruption
(see 3884bfe9661955543ce203c60f9225bbdf33f6bb), because vfork now don't
use the stack.
The xattr system calls are required for the SE Android userspace in
order to get and set file security contexts. In particular, libselinux
requires these calls.
Change-Id: I78f5eb3d8f3384aed0a5e7c6a6f001781d982017