linux-kernel - Re: [PATCH 4/5 v3] ftrace/x86_32: Clean up ftrace_regs

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Message-ID: <CA+55aFxzey_vk+aFpS3L9CUr47r1W5TOUwHX15MJnKfREN20=A@mail.gmail.com>
Date:   Thu, 16 Mar 2017 12:30:25 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...capital.net>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH 4/5 v3] ftrace/x86_32: Clean up ftrace_regs_caller

On Thu, Mar 16, 2017 at 12:24 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
>         popl    %ds
>         popl    %es
>         popl    %fs
>         popl    %gs

Do you even need these? Can they be changed by ftrace?

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.

                Linus