powerpc/kprobes: Clean up jprobe detection in livepatch handler

In commit c05b8c4474 ("powerpc/kprobes: Skip livepatch_handler() for
jprobes"), we added a helper is_current_kprobe_addr() to help detect if
the modified regs->nip was due to a jprobe or livepatch. Masami felt
that the function name was not quite clear. To that end, this patch
renames is_current_kprobe_addr() to __is_active_jprobe() and adds a
comment to (hopefully) better clarify the purpose of this helper. The
helper has also now been moved to kprobes-ftrace.c so that it is only
available for KPROBES_ON_FTRACE.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/kprobes-ftrace.c

@@ -25,6 +25,17 @@
 #include <linux/preempt.h>
 #include <linux/ftrace.h>
 
+/*
+ * This is called from ftrace code after invoking registered handlers to
+ * disambiguate regs->nip changes done by jprobes and livepatch. We check if
+ * there is an active jprobe at the provided address (mcount location).
+ */
+int __is_active_jprobe(unsigned long addr)
+{
+	struct kprobe *p = kprobe_running();
+	return (p && (unsigned long)p->addr == addr) ? 1 : 0;
+}
+
 static nokprobe_inline
 int __skip_singlestep(struct kprobe *p, struct pt_regs *regs,
 		      struct kprobe_ctlblk *kcb, unsigned long orig_nip)

arch/powerpc/kernel/kprobes.c

@@ -43,12 +43,6 @@ DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 
 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
 
-int is_current_kprobe_addr(unsigned long addr)
-{
-	struct kprobe *p = kprobe_running();
-	return (p && (unsigned long)p->addr == addr) ? 1 : 0;
-}
-
 bool arch_within_kprobe_blacklist(unsigned long addr)
 {
 	return  (addr >= (unsigned long)__kprobes_text_start &&

arch/powerpc/kernel/trace/ftrace_64_mprofile.S

@@ -110,9 +110,9 @@ ftrace_call:
 	/* NIP has not been altered, skip over further checks */
 	beq	1f
 
-	/* Check if there is an active kprobe on us */
+	/* Check if there is an active jprobe on us */
 	subi	r3, r14, 4
-	bl	is_current_kprobe_addr
+	bl	__is_active_jprobe
 	nop
 
 	/*