Re: [for-next][PATCH 11/18] s390/function_graph: Simplify with function_graph_entry()

[Martin Schwidefsky]

On Wed, 21 Nov 2018 19:28:12 -0500
Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:

> From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
> 
> The function_graph_entry() function does the work of calling the function
> graph hook function and the management of the shadow stack, simplifying the
> work done in the architecture dependent prepare_ftrace_return().
> 
> Have s390 use the new code, and remove the shadow stack management as well as
> having to set up the trace structure.
> 
> This is needed to prepare for a fix of a design bug on how the curr_ret_stack
> is used.
> 
> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
> Cc: Julian Wiedmann <jwi@xxxxxxxxxxxxx>
> Cc: linux-s390@xxxxxxxxxxxxxxx
> Cc: stable@xxxxxxxxxx
> Fixes: 03274a3ffb449 ("tracing/fgraph: Adjust fgraph depth before calling trace return callback")
> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>

A quick test showed that the patch series works fine on s390.
Acked-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>

> ---
>  arch/s390/kernel/ftrace.c | 13 ++-----------
>  1 file changed, 2 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
> index 84be7f02d0c2..39b13d71a8fe 100644
> --- a/arch/s390/kernel/ftrace.c
> +++ b/arch/s390/kernel/ftrace.c
> @@ -203,22 +203,13 @@ device_initcall(ftrace_plt_init);
>   */
>  unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip)
>  {
> -	struct ftrace_graph_ent trace;
> -
>  	if (unlikely(ftrace_graph_is_dead()))
>  		goto out;
>  	if (unlikely(atomic_read(&current->tracing_graph_pause)))
>  		goto out;
>  	ip -= MCOUNT_INSN_SIZE;
> -	trace.func = ip;
> -	trace.depth = current->curr_ret_stack + 1;
> -	/* Only trace if the calling function expects to. */
> -	if (!ftrace_graph_entry(&trace))
> -		goto out;
> -	if (ftrace_push_return_trace(parent, ip, &trace.depth, 0,
> -				     NULL) == -EBUSY)
> -		goto out;
> -	parent = (unsigned long) return_to_handler;
> +	if (!function_graph_enter(parent, ip, 0, NULL))
> +		parent = (unsigned long) return_to_handler;
>  out:
>  	return parent;
>  }


-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.