linux-kernel - Re: [PATCH v3 1/1] scripts: add zboot support to extract-vmlinux

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Message-ID: <CAK7LNAT+KBFe2wrfw32PpHHEvko3YkkaPHPPt54Y6VuYt7PHMA@mail.gmail.com>
Date: Wed, 16 Jul 2025 09:14:18 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Jeremy Linton <jeremy.linton@....com>
Cc: linux-kbuild@...r.kernel.org, nathan@...nel.org, nicolas.schier@...ux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/1] scripts: add zboot support to extract-vmlinux

On Tue, Jul 15, 2025 at 7:29 AM Jeremy Linton <jeremy.linton@....com> wrote:
>
> Zboot compressed kernel images are used for arm64 kernels on various
> distros.
>
> extract-vmlinux fails with those kernels because the wrapped image is
> another PE. While this could be a bit confusing, the tools primary
> purpose of unwrapping and decompressing the contained kernel image
> makes it the obvious place for this functionality.
>
> Add a 'file' check in check_vmlinux() that detects a contained PE
> image before trying readelf. Recent (FILES_39, Jun/2020) file
> implementations output something like:
>
> "Linux kernel ARM64 boot executable Image, little-endian, 4K pages"
>
> Which is also a stronger statement than readelf provides so drop that
> part of the comment. At the same time this means that kernel images
> which don't appear to contain a compressed image will be returned
> rather than reporting an error. Which matches the behavior for
> existing ELF files.
>
> The extracted PE image can then be inspected, or used as would any
> other kernel PE.
>
> Signed-off-by: Jeremy Linton <jeremy.linton@....com>

Applied to linux-kbuild.
Thanks.


> ---
>  scripts/extract-vmlinux | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/scripts/extract-vmlinux b/scripts/extract-vmlinux
> index 8995cd304e6e..189956b5a5c8 100755
> --- a/scripts/extract-vmlinux
> +++ b/scripts/extract-vmlinux
> @@ -12,13 +12,12 @@
>
>  check_vmlinux()
>  {
> -       # Use readelf to check if it's a valid ELF
> -       # TODO: find a better to way to check that it's really vmlinux
> -       #       and not just an elf
> -       readelf -h $1 > /dev/null 2>&1 || return 1
> -
> -       cat $1
> -       exit 0
> +       if file "$1" | grep -q 'Linux kernel.*boot executable' ||
> +               readelf -h "$1" > /dev/null 2>&1
> +       then
> +               cat "$1"
> +               exit 0
> +       fi
>  }
>
>  try_decompress()
> --
> 2.50.1
>


-- 
Best Regards
Masahiro Yamada