From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1754217AbdCOXPG (ORCPT <rfc822;w@1wt.eu>);
        Wed, 15 Mar 2017 19:15:06 -0400
Received: from mail.kernel.org ([198.145.29.136]:45448 "EHLO mail.kernel.org"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1754195AbdCOXOD (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Wed, 15 Mar 2017 19:14:03 -0400
Date: Wed, 15 Mar 2017 19:13:58 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [RFC][PATCH 5/5] ftrace/x86-32: Add -mfentry support to x86_32
 with DYNAMIC_FTRACE set
Message-ID: <20170315191358.024ea325@gandalf.local.home>
In-Reply-To: <20170315215545.co7elr7b3lguwaiu@treble>
References: <20170315195527.703131481@goodmis.org>
        <20170315200255.828608428@goodmis.org>
        <20170315215545.co7elr7b3lguwaiu@treble>
X-Mailer: Claws Mail 3.14.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Wed, 15 Mar 2017 16:55:45 -0500
Josh Poimboeuf <jpoimboe@redhat.com> wrote:

> On Wed, Mar 15, 2017 at 03:55:32PM -0400, Steven Rostedt wrote:
> > +#ifdef USING_FRAME_POINTER
> > +# ifdef CC_USING_FENTRY
> > +	/*
> > +	 * Frame pointers are of ip followed by bp.
> > +	 * Since fentry is an immediate jump, we are left with
> > +	 * parent-ip, function-ip. We need to add a frame with
> > +	 * parent-ip followed by ebp.
> > +	 */
> > +	pushl 4(%esp)				/* parent ip */
> >  	pushl %ebp
> >  	movl %esp, %ebp
> > -
> > +	pushl 2*4(%esp)				/* function ip */
> > +# endif
> > +	/* For mcount, the function ip is directly above */
> > +	pushl %ebp
> > +	movl %esp, %ebp
> > +#endif  
> 
> More vertical operand alignment issues.
> 
> > @@ -85,6 +140,10 @@ ENTRY(ftrace_regs_caller)
> >  	pushl	%edx
> >  	pushl	%ecx
> >  	pushl	%ebx
> > +#ifndef USING_FRAME_POINTER
> > +	/* Load 4 off of the parent ip addr into ebp */
> > +	lea	14*4(%esp), %ebp
> > +#endif  
> 
> Instead of:
> 
> 	#ifndef USING_FRAME_POINTER
> 	
> Shouldn't it be:
> 
> 	#ifdef CC_USING_FENTRY
> 
> ?
> 
> Otherwise, if I'm reading it right, with fentry and
> CONFIG_FRAME_POINTER=y, ebp will lead to the grandparent's ip instead of
> the parent's ip.

Yep I think you're right. I original added frame pointer setup for the
parent on CC_USING_FENTRY and FRAME_POINTER but that got ugly, this may
be leftover from that.

Thanks, will update.

-- Steve