x86, mm, kprobes: fault.c, simplify notify_page_fault()

Impact: cleanup

Remove an #ifdef from notify_page_fault(). The function still
compiles to nothing in the !CONFIG_KPROBES case.

Introduce kprobes_built_in() and kprobe_fault_handler() helpers
to allow this - they returns 0 if !CONFIG_KPROBES.

No code changed:

   text	   data	    bss	    dec	    hex	filename
   4618	     32	     24	   4674	   1242	fault.o.before
   4618	     32	     24	   4674	   1242	fault.o.after

Cc: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/mm/fault.c

@@ -68,11 +68,10 @@ static inline int kmmio_fault(struct pt_regs *regs, unsigned long addr)
 
 static inline int notify_page_fault(struct pt_regs *regs)
 {
-#ifdef CONFIG_KPROBES
 	int ret = 0;
 
 	/* kprobe_running() needs smp_processor_id() */
-	if (!user_mode_vm(regs)) {
+	if (kprobes_built_in() && !user_mode_vm(regs)) {
 		preempt_disable();
 		if (kprobe_running() && kprobe_fault_handler(regs, 14))
 			ret = 1;
@@ -80,9 +79,6 @@ static inline int notify_page_fault(struct pt_regs *regs)
 	}
 
 	return ret;
-#else
-	return 0;
-#endif
 }
 
 /*

include/linux/kprobes.h

@@ -182,6 +182,14 @@ struct kprobe_blackpoint {
 DECLARE_PER_CPU(struct kprobe *, current_kprobe);
 DECLARE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 
+/*
+ * For #ifdef avoidance:
+ */
+static inline int kprobes_built_in(void)
+{
+	return 1;
+}
+
 #ifdef CONFIG_KRETPROBES
 extern void arch_prepare_kretprobe(struct kretprobe_instance *ri,
 				   struct pt_regs *regs);
@@ -271,8 +279,16 @@ void unregister_kretprobes(struct kretprobe **rps, int num);
 void kprobe_flush_task(struct task_struct *tk);
 void recycle_rp_inst(struct kretprobe_instance *ri, struct hlist_head *head);
 
-#else /* CONFIG_KPROBES */
+#else /* !CONFIG_KPROBES: */
 
+static inline int kprobes_built_in(void)
+{
+	return 0;
+}
+static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr)
+{
+	return 0;
+}
 static inline struct kprobe *get_kprobe(void *addr)
 {
 	return NULL;