linux-kernel - Re: [PATCH] arm64: remove special treatment for the link order of head.o

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Message-ID: <ZBovCrMXJk7NPISp@aurel32.net>
Date:   Tue, 21 Mar 2023 23:26:18 +0100
From:   Aurelien Jarno <aurelien@...el32.net>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-arch@...r.kernel.org,
        Ard Biesheuvel <ardb@...nel.org>,
        Nicolas Schier <nicolas@...sle.eu>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: remove special treatment for the link order of
 head.o

Hi,

On 2022-10-13 08:35, Masahiro Yamada wrote:
> In the previous discussion (see the Link tag), Ard pointed out that
> arm/arm64/kernel/head.o does not need any special treatment - the only
> piece that must appear right at the start of the binary image is the
> image header which is emitted into .head.text.
> 
> The linker script does the right thing to do. The build system does
> not need to manipulate the link order of head.o.
> 
> Link: https://lore.kernel.org/lkml/CAMj1kXH77Ja8bSsq2Qj8Ck9iSZKw=1F8Uy-uAWGVDm4-CG=EuA@mail.gmail.com/
> Suggested-by: Ard Biesheuvel <ardb@...nel.org>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
> 
>  scripts/head-object-list.txt | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/scripts/head-object-list.txt b/scripts/head-object-list.txt
> index b16326a92c45..f226e45e3b7b 100644
> --- a/scripts/head-object-list.txt
> +++ b/scripts/head-object-list.txt
> @@ -15,7 +15,6 @@ arch/alpha/kernel/head.o
>  arch/arc/kernel/head.o
>  arch/arm/kernel/head-nommu.o
>  arch/arm/kernel/head.o
> -arch/arm64/kernel/head.o
>  arch/csky/kernel/head.o
>  arch/hexagon/kernel/head.o
>  arch/ia64/kernel/head.o

This patch causes a significant increase of the arch/arm64/boot/Image
size. For instance the generic arm64 Debian kernel went from 31 to 39 MB
after this patch has been applied to the 6.1 stable tree.

In turn this causes issues with some bootloaders, for instance U-Boot on
a Raspberry Pi limits the kernel size to 36 MB.

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@...el32.net                 http://www.aurel32.net