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

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Message-ID: <20160803031233.b73xz5jftxj7crqh@treble>
Date:	Tue, 2 Aug 2016 22:12:33 -0500
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	"H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Brian Gerst <brgerst@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Byungchul Park <byungchul.park@....com>
Subject: Re: [PATCH 05/19] x86/dumpstack: fix function graph tracing stack
 dump reliability issues

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@...hat.com> 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