linux-kernel - Re: [PATCH 1/2] modpost: don't add warnings for LTO-generated symbols

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Date:   Mon, 5 Feb 2018 07:50:01 -0800
From:   Andi Kleen <ak@...ux.intel.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Jessica Yu <jeyu@...nel.org>, Kees Cook <keescook@...omium.org>,
        nico@...aro.org, linux-kernel@...r.kernel.org,
        Wanlong Gao <wanlong.gao@...il.com>,
        Luis de Bethencourt <luisbg@...nel.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>
Subject: Re: [PATCH 1/2] modpost: don't add warnings for LTO-generated symbols

On Mon, Feb 05, 2018 at 04:12:52PM +0100, Arnd Bergmann wrote:
> WARNING: vmlinux.o(.data+0x12e0): Section mismatch in reference from the variable pfkey_net_ops.lto_priv.2992 to the function .init.text:pfkey_net_init.lto_priv.2977()
> The variable pfkey_net_ops.lto_priv.2992 references
> the function __init pfkey_net_init.lto_priv.2977()
> If the reference is valid then annotate the
> variable with __init* or __refdata (see linux/init.h) or name the variable:
> *_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

A better fix would be to ensure modpost always runs on already LD_FINALed
objects, so it never sees LTO.

Otherwise you would need to teach modpost about the LTO symbol table
and some other magic. I did that once, but it turned out to be very
ugly.

-Andi