x86/ftrace: Support objtool vmlinux.o validation in ftrace_64.S

With objtool vmlinux.o validation of return_to_handler(), now that
objtool has visibility inside the retpoline, jumping from EMPTY state to
a proper function state results in a stack state mismatch.

return_to_handler() is actually quite normal despite the underlying
magic.  Just annotate it as a normal function.

Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/14f48e623f61dbdcd84cf27a56ed8ccae73199ef.1611263462.git.jpoimboe@redhat.com

diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S
index 1bf568d901b1bc1ce806fa73c0ef4b0fa8ce8f72..7c273846c68774471f7deefe9630b30bc7ef6f7d 100644 (file)
--- a/arch/x86/kernel/ftrace_64.S
+++ b/arch/x86/kernel/ftrace_64.S
@@ -334,8 +334,7 @@ SYM_FUNC_START(ftrace_graph_caller)
        retq
 SYM_FUNC_END(ftrace_graph_caller)
 
-SYM_CODE_START(return_to_handler)
-       UNWIND_HINT_EMPTY
+SYM_FUNC_START(return_to_handler)
        subq  $24, %rsp
 
        /* Save the return values */
@@ -350,5 +349,5 @@ SYM_CODE_START(return_to_handler)
        movq (%rsp), %rax
        addq $24, %rsp
        JMP_NOSPEC rdi
-SYM_CODE_END(return_to_handler)
+SYM_FUNC_END(return_to_handler)
 #endif