linux-kernel - Re: [PATCH v2 08/59] x86/build: Ensure proper function alignment

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Message-ID: <CAHk-=whRetwx+5Bjiee+T+Nyyi8EiZ17SM3AL8jJnXuA+WjQyQ@mail.gmail.com>
Date:   Mon, 12 Sep 2022 10:09:38 -0400
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
        x86@...nel.org, Tim Chen <tim.c.chen@...ux.intel.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Johannes Wikner <kwikner@...z.ch>,
        Alyssa Milburn <alyssa.milburn@...ux.intel.com>,
        Jann Horn <jannh@...gle.com>, "H.J. Lu" <hjl.tools@...il.com>,
        Joao Moreira <joao.moreira@...el.com>,
        Joseph Nuzman <joseph.nuzman@...el.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Juergen Gross <jgross@...e.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH v2 08/59] x86/build: Ensure proper function alignment

On Mon, Sep 5, 2022 at 6:07 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Fri, Sep 02, 2022 at 11:08:54AM -0700, Linus Torvalds wrote:
>
> > Let's just do this right.
>
> Something like so then?

Sorry, I dropped this due to travel.

The patch looks sane, the only thing I worry a bit about is

> +config FUNCTION_ALIGNMENT
> +       int
> +       default 64 if FUNCTION_ALIGNMENT_64B
..
> +       default 0

Is '0' even a valid value then for things like

> +#define __ALIGN                        .balign CONFIG_FUNCTION_ALIGNMENT
> +#define __ALIGN_STR            __stringify(__ALIGN)

because it doesn't really seem like a sensible byte alignment.

Maybe "default 4" would be a safer choice?

                   Linus