kprobes/x86-64: Allow to reenter probe on post_handler

Allow to reenter probe on the post_handler of another probe on x86-64,
because x86-64 already allows reentering int3.
In that case, reentered probe just increases kp.nmissed and returns.
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
LKML-Reference: <20090827172304.8246.4822.stgit@localhost.localdomain>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

arch/x86/kernel/kprobes.c

@@ -463,17 +463,6 @@ static int __kprobes reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
 {
 	switch (kcb->kprobe_status) {
 	case KPROBE_HIT_SSDONE:
-#ifdef CONFIG_X86_64
-		/* TODO: Provide re-entrancy from post_kprobes_handler() and
-		 * avoid exception stack corruption while single-stepping on
-		 * the instruction of the new probe.
-		 */
-		arch_disarm_kprobe(p);
-		regs->ip = (unsigned long)p->addr;
-		reset_current_kprobe();
-		preempt_enable_no_resched();
-		break;
-#endif
 	case KPROBE_HIT_ACTIVE:
 		save_previous_kprobe(kcb);
 		set_current_kprobe(p, regs, kcb);