kprobes: introduce weak arch_check_ftrace_location() helper function

Introduce weak arch_check_ftrace_location() helper function which
architectures can override in order to implement handling of kprobes
on function tracer call sites on their own, without depending on
common code or implementing the KPROBES_ON_FTRACE feature.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

include/linux/kprobes.h

@@ -335,6 +335,7 @@ extern void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
 extern int arch_prepare_kprobe_ftrace(struct kprobe *p);
 #endif
 
+int arch_check_ftrace_location(struct kprobe *p);
 
 /* Get the kprobe at this addr (if any) - called with preemption disabled */
 struct kprobe *get_kprobe(void *addr);

kernel/kprobes.c

@@ -1410,16 +1410,10 @@ static inline int check_kprobe_rereg(struct kprobe *p)
 	return ret;
 }
 
-static int check_kprobe_address_safe(struct kprobe *p,
-				     struct module **probed_mod)
+int __weak arch_check_ftrace_location(struct kprobe *p)
 {
-	int ret = 0;
 	unsigned long ftrace_addr;
 
-	/*
-	 * If the address is located on a ftrace nop, set the
-	 * breakpoint to the following instruction.
-	 */
 	ftrace_addr = ftrace_location((unsigned long)p->addr);
 	if (ftrace_addr) {
 #ifdef CONFIG_KPROBES_ON_FTRACE
@@ -1431,7 +1425,17 @@ static int check_kprobe_address_safe(struct kprobe *p,
 		return -EINVAL;
 #endif
 	}
+	return 0;
+}
 
+static int check_kprobe_address_safe(struct kprobe *p,
+				     struct module **probed_mod)
+{
+	int ret;
+
+	ret = arch_check_ftrace_location(p);
+	if (ret)
+		return ret;
 	jump_label_lock();
 	preempt_disable();