Re: [PATCH 16/21] x86/ftrace: Support objtool vmlinux.o validation in ftrace_64.S

[Steven Rostedt]

On Thu, 14 Jan 2021 13:40:12 -0600
Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote:

> 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.

If you say so ;-)

Acked-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>

-- Steve

> 
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> ---
>  arch/x86/kernel/ftrace_64.S | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S
> index 1bf568d901b1..7c273846c687 100644
> --- 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