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 S1753299AbdCPTuM (ORCPT <rfc822;w@1wt.eu>);
        Thu, 16 Mar 2017 15:50:12 -0400
Received: from mail.kernel.org ([198.145.29.136]:43736 "EHLO mail.kernel.org"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1752537AbdCPTuL (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 16 Mar 2017 15:50:11 -0400
Date: Thu, 16 Mar 2017 15:50:06 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux Kernel Mailing List <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>,
        Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: [PATCH 4/5 v3] ftrace/x86_32: Clean up ftrace_regs_caller
Message-ID: <20170316155006.1f0ef5fe@gandalf.local.home>
In-Reply-To: <CA+55aFxzey_vk+aFpS3L9CUr47r1W5TOUwHX15MJnKfREN20=A@mail.gmail.com>
References: <20170316172008.086705006@goodmis.org>
        <20170316172056.576095199@goodmis.org>
        <CA+55aFwmLXLMdvM_Bur9_j6LcaHwHvng-kXEw+rUBgYKbS_6ZA@mail.gmail.com>
        <20170316140913.653af64d@gandalf.local.home>
        <CA+55aFwuqLGXKX=CkK6Ywoh-JNXdXtqdJhonqubRQQSEroc=dA@mail.gmail.com>
        <20170316151932.5b9167b5@gandalf.local.home>
        <20170316152431.05316146@gandalf.local.home>
        <CA+55aFxzey_vk+aFpS3L9CUr47r1W5TOUwHX15MJnKfREN20=A@mail.gmail.com>
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 Thu, 16 Mar 2017 12:30:25 -0700
Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Thu, Mar 16, 2017 at 12:24 PM, Steven Rostedt <rostedt@goodmis.org> wrote:
> >         popl    %ds
> >         popl    %es
> >         popl    %fs
> >         popl    %gs  
> 
> Do you even need these? Can they be changed by ftrace?

ftrace no, kprobes, maybe.

> 
> And see the previous email about not touching the original location at
> all, adn just duplicating that entry, avoiding all the need for
> shuffling. I *really* hope that ftrace doesn't depend on changing the
> return %eip on the stack. That would be truly nasty.

How do you think the live patching works?

-- Steve