x86/ftrace: Add UNWIND_HINT_FUNC annotation for ftrace_stub

stable inclusion
from stable-v5.10.133
commit 95d89ec7dba56f7974aeda2beace2112df9f1418
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5PTAS
CVE: CVE-2022-29900,CVE-2022-23816,CVE-2022-29901

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=95d89ec7dba56f7974aeda2beace2112df9f1418

--------------------------------

commit 18660698 upstream.

Prevent an unreachable objtool warning after the sibling call detection
gets improved.  ftrace_stub() is basically a function, annotate it as
such.
Acked-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/6845e1b2fb0723a95740c6674e548ba38c5ea489.1611263461.git.jpoimboe@redhat.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NLin Yujun <linyujun809@huawei.com>
Reviewed-by: NZhang Jianhua <chris.zjh@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/x86/kernel/ftrace_64.S

@@ -173,6 +173,7 @@ SYM_INNER_LABEL(ftrace_graph_call, SYM_L_GLOBAL)
  * It is also used to copy the RET for trampolines.
  */
 SYM_INNER_LABEL_ALIGN(ftrace_stub, SYM_L_WEAK)
+	UNWIND_HINT_FUNC
 	RET
 SYM_FUNC_END(ftrace_epilogue)