linux-kernel - Re: [PATCH v4 06/27] x86/doublefault: Remove memmove() call

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Message-ID: <CALCETrWmnkrHi1FYFLvj5G7SrmN+BrwLgKyt=NBtd-EOoRyeSQ@mail.gmail.com>
Date:   Fri, 21 Feb 2020 11:10:05 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Greg KH <gregkh@...uxfoundation.org>, gustavo@...eddedor.com,
        Thomas Gleixner <tglx@...utronix.de>, paulmck@...nel.org,
        Josh Triplett <josh@...htriplett.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Andrew Lutomirski <luto@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [PATCH v4 06/27] x86/doublefault: Remove memmove() call

On Fri, Feb 21, 2020 at 5:50 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> Use of memmove() in #DF is problematic when you consider tracing and
> other instrumentation.
>
> Remove the memmove() call and simply write out what need doing; Boris
> argues the ranges should not overlap.
>
> Survives selftests/x86, specifically sigreturn_64.
>
> (Andy ?!)

Acked-by: Andy Lutomirski <luto@...nel.org>

Even ignoring the tracing issue, I think this is nicer than the original code.