Re: [PATCH 05/19] x86/dumpstack: fix function graph tracing stack dump reliability issues

[Josh Poimboeuf]

On Tue, Aug 02, 2016 at 10:59:36PM -0400, Steven Rostedt wrote:
> On Tue, 2 Aug 2016 21:50:12 -0500
> Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote:
> 
> 
> > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > index 1e814ae..fc508a7 100644
> > --- a/include/linux/ftrace.h
> > +++ b/include/linux/ftrace.h
> > @@ -795,7 +795,9 @@ struct ftrace_ret_stack {
> >  	unsigned long func;
> >  	unsigned long long calltime;
> >  	unsigned long long subtime;
> > +#if defined(CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST) && !defined(CC_USING_FENTRY)
> 
> We need to make a new defined in ftrace.h:
> 
> #if defined(CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST) && !defined(CC_USING_FENTRY)
> # define HAVE_FUNCTION_GRAPH_FP_TEST
> #endif
> 
> And use that instead of this && complexity.
> 
> Or better yet, get rid of the CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST define
> and only have HAVE_FUNCTION_GRAPH_FP_TEST defined in the asm/ftrace.h
> in each arch. Then, x86 could just do;
> 
> #ifndef CC_USING_FENTRY
> # define HAVE_FUNCTION_GRAPH_FP_TEST
> #endif

Sounds good.  I was thinking I could also add a similar define to
indicate whether an arch passes the return address stack pointer to
ftrace_push_return_trace().  HAVE_FUNCTION_GRAPH_RET_ADDR_PTR?

-- 
Josh