Re: [gentoo-dev] [PATCH 5/6] dist-kernel-utils.eclass: Support dracut's uefi=yes option

[Michał Górny]

On Wed, 2021-01-13 at 11:47 -0600, Matthew Thode wrote:
> On 21-01-13 15:35:15, Michał Górny wrote:
> > Support dracut's uefi=yes configuration option that creates a combined
> > UEFI stub, kernel and initramfs in a single UEFI executable.  If such
> > an output is detected, install it in place of the actual kernel image
> > and stub out the duplicate initrd to save space.
> >
> > Signed-off-by: Michał Górny <mgorny@g.o>
> > ---
> >  eclass/dist-kernel-utils.eclass | 31 ++++++++++++++++++++++++++++++-
> >  1 file changed, 30 insertions(+), 1 deletion(-)
> >
> > diff --git a/eclass/dist-kernel-utils.eclass b/eclass/dist-kernel-utils.eclass
> > index d65dc0924b40..50ad15f8b1fd 100644
> > --- a/eclass/dist-kernel-utils.eclass
> > +++ b/eclass/dist-kernel-utils.eclass
> > @@ -41,8 +41,20 @@ dist-kernel_build_initramfs() {
> >  	local output=${1}
> >  	local version=${2}
> >  
> >
> >
> >
> > +	local rel_image_path=$(dist-kernel_get_image_path)
> > +	local image=${output%/*}/${rel_image_path##*/}
> > +
> > +	local args=(
> > +		--force
> > +		# if uefi=yes is used, dracut needs to locate the kernel image
> > +		--kernel-image "${image}"
> > +
> > +		# positional arguments
> > +		"${output}" "${version}"
> > +	)
> > +
> >  	ebegin "Building initramfs via dracut"
> > -	dracut --force "${output}" "${version}"
> > +	dracut "${args[@]}"
> >  	eend ${?} || die -n "Building initramfs failed"
> >  }
> >  
> >
> >
> >
> > @@ -85,6 +97,23 @@ dist-kernel_install_kernel() {
> >  	local image=${2}
> >  	local map=${3}
> >  
> >
> >
> >
> > +	# if dracut is used in eufi=yes mode, initrd will actually
> > +	# be a combined kernel+initramfs UEFI executable.  we can easily
> > +	# recognize it by PE magic (vs cpio for a regular initramfs)
> > +	local initrd=${image%/*}/initrd
> > +	local magic
> > +	[[ -s ${initrd} ]] && read -n 2 magic < "${initrd}"
> > +	if [[ ${magic} == MZ ]]; then
>
> This magic header is matched by both the kernel and the new uefi
> executible.  I think a better check would be...
>
> if file "${image_path}" | grep -q 'EFI application'; then

...but we're not testing image but initrd which can't be the kernel
otherwise.

>
> > +		einfo "Combined UEFI kernel+initramfs executable found"
> > +		# install the combined executable in place of kernel
> > +		image=${initrd}.uefi
> > +		mv "${initrd}" "${image}" || die
> > +		# put an empty file in place of initrd.  installing a duplicate
> > +		# file would waste disk space, and removing it entirely provokes
> > +		# kernel-install to regenerate it via dracut.
> > +		> "${initrd}"
> > +	fi
> > +
> >  	ebegin "Installing the kernel via installkernel"
> >  	# note: .config is taken relatively to System.map;
> >  	# initrd relatively to bzImage
> > --
> > 2.30.0
>
> I want to make sure you are not overwriting the original kernel image,
> if you do then subsiquent --config runs will include the kernel image,
> making the final image grow.
>
> In order to avoid that I did some file juggling, but it looks like it's
> cleaner here.

I still don't understand why it has been overwriting the kernel for you.

>
> https://gist.github.com/prometheanfire/aeffa1c3f92d3d2af312b3b6915051fb
> 'worked' but was kinda unclean.
>
>

-- 
Best regards,
Michał Górny