linux-kernel - Re: [PATCH v2 2/3] MIPS: Move kernel head into a standalone section

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Message-ID: <20200527115354.GC13965@alpha.franken.de>
Date:   Wed, 27 May 2020 13:53:54 +0200
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Jiaxun Yang <jiaxun.yang@...goat.com>
Cc:     linux-mips@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        Borislav Petkov <bp@...e.de>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Fangrui Song <maskray@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] MIPS: Move kernel head into a standalone section

On Wed, May 27, 2020 at 02:34:33PM +0800, Jiaxun Yang wrote:
> That's what already done by Arm64 and other architectures.
> That would allow us put more things like PE headers safely into
> the header.
> 
> Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>
> ---
>  arch/mips/kernel/head.S        | 4 ++--
>  arch/mips/kernel/vmlinux.lds.S | 8 ++++++--
>  2 files changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/mips/kernel/head.S b/arch/mips/kernel/head.S
> index c7c2795837e7..8081a905a71c 100644
> --- a/arch/mips/kernel/head.S
> +++ b/arch/mips/kernel/head.S
> @@ -59,6 +59,8 @@
>  #endif
>  	.endm
>  
> +	__HEAD
> +_head:
>  #ifndef CONFIG_NO_EXCEPT_FILL
>  	/*
>  	 * Reserved space for exception handlers.

I'm adding the missing piece, why this change ist broken:

         * Necessary for machines which link their kernels at KSEG0.

by putting something in front of that will probably break platforms making
use of "feature". If we can make sure, we don't need it anymore, we should
first remove this and then add __HEAD part.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]