fprobe: Pass return address to the handlers

Pass return address as 'ret_ip' to the fprobe entry and return handlers
so that the fprobe user handler can get the reutrn address without
analyzing arch-dependent pt_regs.

Link: https://lore.kernel.org/all/168507467664.913472.11642316698862778600.stgit@mhiramat.roam.corp.google.com/

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

kernel/kprobes.c

@@ -2127,6 +2127,7 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
 NOKPROBE_SYMBOL(pre_handler_kretprobe);
 
 static void kretprobe_rethook_handler(struct rethook_node *rh, void *data,
+				      unsigned long ret_addr,
 				      struct pt_regs *regs)
 {
 	struct kretprobe *rp = (struct kretprobe *)data;