linux-kernel - Re: [patch V4 part 2 01/18] x86/entry/64: Move non entry code into .text section

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Message-ID: <CALCETrWJDdxnP5pJQinMkyL+mb3th1tWGY7psYqod8nDnrV2YQ@mail.gmail.com>
Date:   Fri, 8 May 2020 16:53:05 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>
Subject: Re: [patch V4 part 2 01/18] x86/entry/64: Move non entry code into
 .text section

On Tue, May 5, 2020 at 7:14 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> All ASM code which is not part of the entry functionality can move out into
> the .text section. No reason to keep it in the non-instrumentable entry
> section.

Ick.  How about just moving that code into another file altogether?

> +.pushsection .text, "ax"
>  SYM_FUNC_START(native_load_gs_index)
>         FRAME_BEGIN
>         pushfq
> @@ -1058,6 +1063,7 @@ SYM_FUNC_START(native_load_gs_index)
>         ret
>  SYM_FUNC_END(native_load_gs_index)
>  EXPORT_SYMBOL(native_load_gs_index)
> +.popsection

native_load_gs_index is toast if it gets instrumented in the wrong way.