Re: [PATCH 7/8] dracut: add support for cross initrd generation

["'MOESSBAUER, Felix' via isar-users" <isar-users@googlegroups.com>]

On Tue, 2026-09-15 at 12:01 +0200, Felix Moessbauer wrote:
> For cross-initrd generation, a cross variant of the ldd tool needs to
> be provided. As there is no such tool, but this is THE performance
> critical part (it needs to scan each binary and all transitive dependencies),
> we provide a custom one which uses readelf to determine the shared library
> dependencies.
> 
> Signed-off-by: Felix Moessbauer <felix.moessbauer@siemens.com>
> ---
>  meta/classes-recipe/host-tooling.bbclass      |  4 +-
>  meta/classes-recipe/initrd-dracut.bbclass     | 36 +++++++++-
>  meta/classes-recipe/rootfs.bbclass            |  4 +-
>  .../dracut-cross-ldd/dracut-cross-ldd.bb      | 16 +++++
>  .../dracut-cross-ldd/files/dracut-cross-ldd   | 65 +++++++++++++++++++
>  5 files changed, 121 insertions(+), 4 deletions(-)
>  create mode 100644 meta/recipes-devtools/dracut-cross-ldd/dracut-cross-ldd.bb
>  create mode 100644 meta/recipes-devtools/dracut-cross-ldd/files/dracut-cross-ldd
> 
> diff --git a/meta/classes-recipe/host-tooling.bbclass b/meta/classes-recipe/host-tooling.bbclass
> index b76f8898..5e81dfda 100644
> --- a/meta/classes-recipe/host-tooling.bbclass
> +++ b/meta/classes-recipe/host-tooling.bbclass
> @@ -5,8 +5,8 @@
>  LICENSE = "gpl-2.0"
>  LIC_FILES_CHKSUM = "file://${LAYERDIR_core}/licenses/COPYING.GPLv2;md5=751419260aa954499f7abaabaa882bbe"
>  
> -HOST_TOOLING_PACKAGES ?= ""
> -HOST_TOOLING_DEPENDS ?= ""
> +HOST_TOOLING_PACKAGES ?= "dracut-core binutils zstd dracut-cross-ldd"
> +HOST_TOOLING_DEPENDS ?= "dracut-cross-ldd"
>  
>  # dependency to build the host-tooling-chroot
>  HOST_TOOLING_DEP ?= "host-tooling-chroot:do_build"
> diff --git a/meta/classes-recipe/initrd-dracut.bbclass b/meta/classes-recipe/initrd-dracut.bbclass
> index 00999b91..ffc71db6 100644
> --- a/meta/classes-recipe/initrd-dracut.bbclass
> +++ b/meta/classes-recipe/initrd-dracut.bbclass
> @@ -56,8 +56,42 @@ def extend_dracut_cmdline(d):
>  ROOTFS_INITRAMFS_GENERATOR_CMDLINE = "dracut --force --kver $kernel_version -L 5 --reproducible"
>  ROOTFS_INITRAMFS_GENERATOR_CMDLINE:append = " ${@ extend_dracut_cmdline(d)}"
>  
> +# Cross-assemble the initramfs, requires preparation of dracut module definitions
> +def dracut_cross_default(d):
> +    return bb.utils.to_boolean(d.getVar('ISAR_CROSS_COMPILE')) \
> +        and bb.utils.to_boolean(d.getVar('ROOTFS_USE_DRACUT')) \
> +        and d.getVar('ROOTFS_ARCH') != d.getVar('HOST_ARCH')
> +
> +ROOTFS_DRACUT_CROSS ??= "${@ '1' if dracut_cross_default(d) else '0' }"
> +ROOTFS_DRACUT_CROSS:bookworm = "0"
> +OVERRIDES:append = "${@':dracut-cross' if bb.utils.to_boolean(d.getVar('ROOTFS_DRACUT_CROSS')) else ''}"
> +
> +ROOTFS_INSTALL_DEPENDS:append:dracut-cross = " ${HOST_TOOLING_DEP}"
> +ROOTFS_INITRAMFS_GENERATOR_CMDLINE:append:dracut-cross = " --sysroot /mnt/rootfs"
> +DRACUT_MOUNTS = ""
> +DRACUT_MOUNTS:append:dracut-cross = " ${ROOTFSDIR}:/mnt/rootfs"
> +DRACUT_ROOTFS = "${ROOTFSDIR}"
> +DRACUT_ROOTFS:dracut-cross = "${WORKDIR}/host-tooling"
> +DRACUT_ENV = "DRACUT_ARCH=${QEMU_ARCH}"
> +DRACUT_ENV:append:dracut-cross = " \
> +    DRACUT_INSTALL=/usr/lib/dracut/dracut-install \
> +    DRACUT_LDD=/usr/libexec/dracut-cross-ldd \
> +"
> +
>  run_initrd_generator() {
>      mods_total="$(find ${ROOTFSDIR}/usr/lib/dracut/modules.d/ -maxdepth 1 -type d | wc -l)"
>      echo "Total number of modules: $mods_total (dracut)"
> -    run_in_chroot "${ROOTFSDIR}" sh -c "${ROOTFS_INITRAMFS_GENERATOR_CMDLINE}"
> +    if [ "${ROOTFS_DRACUT_CROSS}" = "1" ]; then
> +        mkdir -p ${DRACUT_ROOTFS}
> +        run_privileged tar -xf ${HOST_TOOLING_CHROOT} -C ${DRACUT_ROOTFS}

We currently miss a dependency to ${HOST_TOOLING_DEP} here. When
writing this series, the caching was not that efficient to ever hit the
condition.

Will send a v2.

Felix

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