This patch adds kretprobe-booster to kprobes_64.c.

- Changes are based on x86-32.
- Rewrite register saving/restoring code
Signed-off-by: NMasami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>