livepatch: move x86 specific ftrace handler code to arch/x86

The execution flow redirection related implemention in the livepatch
ftrace handler is depended on the specific architecture. This patch
introduces klp_arch_set_pc(like kgdb_arch_set_pc) interface to change
the pt_regs.
Signed-off-by: Li Bin <huawei.libin@huawei.com>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

arch/x86/include/asm/livepatch.h

@@ -22,6 +22,7 @@
 #define _ASM_X86_LIVEPATCH_H
 
 #include <linux/module.h>
+#include <linux/ftrace.h>
 
 #ifdef CONFIG_LIVE_PATCHING
 #ifndef CC_USING_FENTRY
@@ -30,6 +31,10 @@
 extern int klp_write_module_reloc(struct module *mod, unsigned long type,
 				  unsigned long loc, unsigned long value);
 
+static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
+{
+	regs->ip = ip;
+}
 #else
 #error Live patching support is disabled; check CONFIG_LIVE_PATCHING
 #endif

kernel/livepatch/core.c

@@ -272,7 +272,7 @@ static void notrace klp_ftrace_handler(unsigned long ip,
 {
 	struct klp_func *func = ops->private;
 
-	regs->ip = (unsigned long)func->new_func;
+	klp_arch_set_pc(regs, (unsigned long)func->new_func);
 }
 
 static int klp_disable_func(struct klp_func *func)