linux-kernel - Re: [PATCH] kheaders: making headers archive reproducible

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Date:   Thu, 3 Oct 2019 10:08:35 -0400
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Dmitry Goldin <dgoldin@...tonmail.ch>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Ben Hutchings <ben@...adent.org.uk>
Subject: Re: [PATCH] kheaders: making headers archive reproducible

On Thu, Oct 03, 2019 at 10:50:06AM +0900, Masahiro Yamada wrote:
> Hi Dmitry,
> 
> 
> (+CC Ben Hutchings, who might be interested)
> 
> 
> On Sun, Sep 22, 2019 at 10:38 PM Dmitry Goldin <dgoldin@...tonmail.ch> wrote:
> >
> > From: Dmitry Goldin <dgoldin+lkml@...tonmail.ch>
> >
> > In commit 43d8ce9d65a5 ("Provide in-kernel headers to make
> > extending kernel easier") a new mechanism was introduced, for kernels
> > >=5.2, which embeds the kernel headers in the kernel image or a module
> > and exposed them in procfs for use by userland tools.
> >
> > The archive containing the header files has nondeterminism through the
> > header files metadata. This patch normalizes the metadata and utilizes
> > KBUILD_BUILD_TIMESTAMP if provided and otherwise falls back to the
> > default behaviour.
> >
> > In commit f7b101d33046 ("kheaders: Move from proc to sysfs") it was
> > modified to use sysfs and the script for generation of the archive was
> > renamed to what is being patched.
> >
> > Signed-off-by: Dmitry Goldin <dgoldin+lkml@...tonmail.ch>
> > ---
> >  kernel/gen_kheaders.sh | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> 
> Thanks, this produced the deterministic archive for me.
> 

Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>

thanks,

 - Joel


> 
> While you are here, could you also update the following hunk
> in Documentation/kbuild/reproducible-builds.rst
> 
> ---------->8---------------
> The kernel embeds a timestamp in two places:
> 
> * The version string exposed by ``uname()`` and included in
>   ``/proc/version``
> 
> * File timestamps in the embedded initramfs
> ---------->8---------------
> 
> 
> With the documentation updated, I will pick it soon.
> 
> Thank you.
> 
> 
> 
> 
> > diff --git a/kernel/gen_kheaders.sh b/kernel/gen_kheaders.sh
> > index 9ff449888d9c..2e154741e3b2 100755
> > --- a/kernel/gen_kheaders.sh
> > +++ b/kernel/gen_kheaders.sh
> > @@ -71,7 +71,10 @@ done | cpio --quiet -pd $cpio_dir >/dev/null 2>&1
> >  find $cpio_dir -type f -print0 |
> >         xargs -0 -P8 -n1 perl -pi -e 'BEGIN {undef $/;}; s/\/\*((?!SPDX).)*?\*\///smg;'
> >
> > -tar -Jcf $tarfile -C $cpio_dir/ . > /dev/null
> > +# Create archive and try to normalized metadata for reproducibility
> > +tar "${KBUILD_BUILD_TIMESTAMP:+--mtime=$KBUILD_BUILD_TIMESTAMP}" \
> > +    --owner=0 --group=0 --sort=name --numeric-owner \
> > +    -Jcf $tarfile -C $cpio_dir/ . > /dev/null
> >
> >  echo "$src_files_md5" >  kernel/kheaders.md5
> >  echo "$obj_files_md5" >> kernel/kheaders.md5
> > --
> > 2.19.2
> >
> >
> >
> 
> 
> -- 
> Best Regards
> Masahiro Yamada