linux-kernel - Re: [PATCH] x86: Don't clare __force_order in kaslr

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Date:   Fri, 24 Jan 2020 10:24:19 -0800
From:   Andy Lutomirski <luto@...capital.net>
To:     "H.J. Lu" <hjl.tools@...il.com>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Yu-cheng Yu <yu-cheng.yu@...el.com>
Subject: Re: [PATCH] x86: Don't clare __force_order in kaslr_64.c



> On Jan 24, 2020, at 10:18 AM, H.J. Lu <hjl.tools@...il.com> wrote:
> 
> GCC 10 changed the default to -fno-common, which leads to
> 
>  LD      arch/x86/boot/compressed/vmlinux
> ld: arch/x86/boot/compressed/pgtable_64.o:(.bss+0x0): multiple definition of `__force_order'; arch/x86/boot/compressed/kaslr_64.o:(.bss+0x0): first defined here
> make[2]: *** [arch/x86/boot/compressed/Makefile:119: arch/x86/boot/compressed/vmlinux] Error 1
> 
> Since __force_order is already provided in pgtable_64.c, there is no
> need to declare __force_order in kaslr_64.c.

Why does anything actually define that variable?  Surely any actual references are just an outright bug.  Is it needed for LTO?