Re: [PATCH v4 5/8] Provide class for easy custom kernel builds

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2018-02-12 19:56, Alexander Smirnov wrote:
> On 02/11/2018 06:25 PM, Jan Kiszka wrote:
>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>
>> With this class, it becomes almost trivial to replace the distro kernel
>> with a custom build. You just need to inherit linux-kernel, specify the
>> source URI, define via S where the source is unpacked to and provide a
>> defconfig. To switch to a custom kernel recipe,
>> PREFERRED_PROVIDER_virtual/kernel has to be adjusted in local.conf or
>> the distro conf.
>>
>> The approach works internally by first running "make deb-pkg" on the
>> kernel and the repackages the output to make the binary linux-image and
>> linux-header debs act as replacement of their distro packages. This
>> results in a suboptimal technical implementation which may eventually be
>> replaced by an isar-implemented deb-pkg build process. However, this is
>> not expected to affect the user-visible interface of this class.
>>
>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>> ---
>>   meta/classes/linux-kernel.bbclass | 98
>> +++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 98 insertions(+)
>>   create mode 100644 meta/classes/linux-kernel.bbclass
>>
>> diff --git a/meta/classes/linux-kernel.bbclass
>> b/meta/classes/linux-kernel.bbclass
>> new file mode 100644
>> index 0000000..5f4df3f
>> --- /dev/null
>> +++ b/meta/classes/linux-kernel.bbclass
>> @@ -0,0 +1,98 @@
>> +# Custom kernel build
>> +#
>> +# This software is a part of ISAR.
>> +# Copyright (c) Siemens AG, 2018
>> +#
>> +# SPDX-License-Identifier: MIT
>> +
>> +DESCRIPTION ?= "Custom kernel"
>> +PROVIDES = "virtual/kernel"
>> +
>> +inherit dpkg-base
>> +
>> +KERNEL_DEBIAN_DEPENDS ?= "initramfs-tools | linux-initramfs-tool,
>> kmod, linux-base (>= 4.3~)"
>> +KERNEL_HEADERS_DEBIAN_DEPENDS ?= "libc6, libssl1.1, gcc"
>> +KBUILD_DEPENDS ?= "libssl-dev libelf-dev bc"
>> +
>> +REPACK_DIR = "${PP}/repack"
>> +REPACK_LINUX_IMAGE_DIR = "${REPACK_DIR}/linux-image"
>> +REPACK_LINUX_HEADERS_DIR = "${REPACK_DIR}/linux-headers"
>> +
>> +dpkg_runbuild() {
>> +    E="${@ bb.utils.export_proxies(d)}"
>> +    sudo -E chroot ${BUILDCHROOT_DIR} sh -c '
>> +        set -e
>> +
>> +        apt-get install -y -o Debug::pkgProblemResolver=yes \
>> +            --no-install-recommends ${KBUILD_DEPENDS}
>> +
>> +        cd ${PP}/${S}
>> +        cp ../defconfig .config
>> +        make olddefconfig
>> +
>> +        make -j ${@bb.utils.cpu_count() * 2} deb-pkg
>> +
>> +        rm -rf ${REPACK_DIR}
>> +        mkdir -p ${REPACK_DIR}
>> +        mkdir -p ${REPACK_LINUX_IMAGE_DIR}
>> +        mkdir -p ${REPACK_LINUX_HEADERS_DIR}
>> +
>> +        cd ${PP}
>> +        tar xzf linux-${PV}_${PV}-1.debian.tar.gz -C ${REPACK_DIR}
>> +        dpkg-deb -R linux-image-${PV}_${PV}-1_${KERNEL_ARCH}.deb \
>> +            ${REPACK_LINUX_IMAGE_DIR}
>> +        dpkg-deb -R linux-headers-${PV}_${PV}-1_${KERNEL_ARCH}.deb \
>> +            ${REPACK_LINUX_HEADERS_DIR}
>> +
>> +        dpkg-gencontrol -crepack/debian/control \
>> +            -lrepack/debian/changelog \
>> +            -frepack/debian/files \
>> +            -plinux-image-${PV} \
>> +            -P${REPACK_LINUX_IMAGE_DIR} \
>> +            -DPackage="linux-image-${KERNEL_ARCH}" \
>> +            -DSection=kernel \
>> +            -DPriority=required \
>> +            -DProvides="${PN}" \
>> +            -DDepends="${KERNEL_DEBIAN_DEPENDS}"
>> +
>> +        # Add Debian-like link installation to postinst
>> +        touch ${REPACK_LINUX_IMAGE_DIR}/lib/modules/${PV}/.fresh-install
>> +        sed -i ${REPACK_LINUX_IMAGE_DIR}/DEBIAN/postinst \
>> +            -e "/^set -e$/a\\
>> +\\
>> +if [ -f /lib/modules/${PV}/.fresh-install ]; then\\
>> +    change=install\\
>> +else\\
>> +    change=upgrade\\
>> +fi\\
>> +linux-update-symlinks \$change ${PV} /boot/vmlinuz-${PV}\\
>> +rm -f /lib/modules/${PV}/.fresh-install"
>> +
>> +        # Add Debian-like link removal to postrm
>> +        sed -i ${REPACK_LINUX_IMAGE_DIR}/DEBIAN/postrm \
>> +            -e "/^set -e$/a\\
>> +\\
>> +rm -f /lib/modules/${PV}/.fresh-install\\
>> +\\
>> +if [ \"\$1\" != upgrade ] && command -v linux-update-symlinks
>> >/dev/null; then\\
>> +    linux-update-symlinks remove ${PV}  /boot/vmlinuz-${PV}\\
>> +fi"
>> +
>> +        dpkg-gencontrol -crepack/debian/control \
>> +            -lrepack/debian/changelog \
>> +            -frepack/debian/files \
>> +            -plinux-headers-${PV} \
>> +            -P${REPACK_LINUX_HEADERS_DIR} \
>> +            -Vkernel:debarch="${KERNEL_ARCH}" \
>> +            -DPackage="linux-headers-${KERNEL_ARCH}" \
>> +            -DSection=kernel \
>> +            -DDepends="${KERNEL_HEADERS_DEBIAN_DEPENDS}"
>> +
>> +        dpkg-deb -b ${REPACK_LINUX_IMAGE_DIR} \
>> +            linux-image-${KERNEL_ARCH}_${PV}-1_${KERNEL_ARCH}.deb
>> +        rm -f linux-image-${PV}_${PV}-1_${KERNEL_ARCH}.deb
>> +        dpkg-deb -b ${REPACK_LINUX_HEADERS_DIR} \
>> +            linux-headers-${KERNEL_ARCH}_${PV}-1_${KERNEL_ARCH}.deb
>> +        rm -f linux-headers-${PV}_${PV}-1_${KERNEL_ARCH}.deb
>> +    '
>> +}
>>
> 
> What is the benefit of having this script in the class? I see that we
> have separate files for:
> 
>  - buildchroot
>  - kernel modules
> 
> Why this chroot script should be a part of bitbake class? This makes
> debugging much more complicated, because I have no possibility to run
> this script manually from buildchroot (like I could do with build.sh)

I played with it, and it "just" took 6 exports to set up the interface
to script-based build. That will likely not be convenient for debugging
as well (and I never had to call things manually that way, I got all
information from logs), but I can keep that pattern. Will also mean:
back to an include, rather than using a class (no big issue).

> 
> Also formatting style looks nasty here.

That's not going to change unless you suggest some alternative for the
sed-based code injection into postinst/postrm.

Jan

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