d6858c9f45
The U-Boot signing code is a bit of a mess. The problem is that mkimage
determines the public keys to embed into a device tree based on an image
that it is signing. This results in all sorts of contortions: U-Boot has to
be available to the kernel recipe so that it can have the correct public
keys embedded. Then, the signed U-Boot has to be made available to U-Boot's
do_deploy. This same dance is then repeated for SPL. To complicate matters,
signing for U-Boot and U-Boot SPL is optional, so the whole process must be
seamlessly integrated with a non-signed build.
The complexity and interdependency of this process makes it difficult to
extend. For example, it is not possible to install a signed U-Boot binary
into the root filesystem. This is first because u-boot:do_install must run
before linux:do_assemble_fitimage, which must run before u-boot:do_deploy.
But aside from infrastructure issues, installing a signed U-Boot also can't
happen, because the kernel image might have an embedded initramfs
(containing the signed U-Boot).
However, all of this complexity is accidental. It is not necessary to embed
the public keys into U-Boot and sign the kernel in one fell swoop. Instead,
we can sign the kernel, stage it, and sign the staged kernel again to embed
the public keys into U-Boot [1]. This twice-signed kernel serves only to
provide the correct parameters to mkimage, and does not have to be
installed or deployed. By cutting the dependency of
linux:do_assemble_fitimage on u-boot:do_install, we can drastically
simplify the build process, making it much more extensible.
The process of doing this conversion is a bit involved, since the U-Boot
and Linux recipes are so intertwined at the moment. The most major change
is that uboot-sign is no longer inherited by kernel-fitimage. Similarly,
all U-Boot-related tasks have been removed from kernel-fitimage. We add a
new step to the install task to stage the kernel in /sysroot-only. The
logic to disable assemble_fitimage has been removed. We always assemble it,
even if the final fitImage will use a bundled initramfs, because U-Boot
will need it.
On the U-Boot side, much of the churn stems from multiple config support.
Previously, we took a fairly ad-hoc approach to UBOOT_CONFIG and
UBOOT_MACHINE, introducing for loops wherever we needed to deal with them.
However, I have chosen to use a much more structured approach. Each task
which needs to use the build directory uses the following pseudocode:
do_mytask() {
if ${UBOOT_CONFIG}; then
for config, type in zip(${UBOOT_CONFIG}, ${UBOOT_MACHINE}); do
cd ${config}
mytask_helper ${type}
done
else
cd ${B}
mytask_helper ""
fi
}
By explicitly placing the work in mytask_helper, we make it easier to
ensure that everything is covered, and we also allow bbappends files to
more easily extend the task (as otherwise they would need to reimplement
the loop themselves).
[1] It doesn't particularly matter what we sign. Any FIT will do, but I
chose the kernel's because we already went to the trouble of setting it up
with the correct hashes and signatures. In the future, we could create a
"dummy" image and sign that instead, but it would probably have to happen
in the kernel recipe anyway (so we have access to the appropriate
variables).
(From OE-Core rev: 5e12dc911d0c541f43aa6d0c046fb87e8b7c1f7e)
Signed-off-by: Sean Anderson <sean.anderson@seco.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Poky
Poky is an integration of various components to form a pre-packaged build system and development environment which is used as a development and validation tool by the Yocto Project. It features support for building customised embedded style device images and custom containers. There are reference demo images ranging from X11/GTK+ to Weston, commandline and more. The system supports cross-architecture application development using QEMU emulation and a standalone toolchain and SDK suitable for IDE integration.
Additional information on the specifics of hardware that Poky supports is available in README.hardware. Further hardware support can easily be added in the form of BSP layers which extend the systems capabilities in a modular way. Many layers are available and can be found through the layer index.
As an integration layer Poky consists of several upstream projects such as BitBake, OpenEmbedded-Core, Yocto documentation, the 'meta-yocto' layer which has configuration and hardware support components. These components are all part of the Yocto Project and OpenEmbedded ecosystems.
The Yocto Project has extensive documentation about the system including a reference manual which can be found at https://docs.yoctoproject.org/
OpenEmbedded is the build architecture used by Poky and the Yocto project. For information about OpenEmbedded, see the OpenEmbedded website.
Contribution Guidelines
The project works using a mailing list patch submission process. Patches should be sent to the mailing list for the repository the components originate from (see below). Throughout the Yocto Project, the README files in the component in question should detail where to send patches, who the maintainers are and where bugs should be reported.
A guide to submitting patches to OpenEmbedded is available at:
https://www.openembedded.org/wiki/How_to_submit_a_patch_to_OpenEmbedded
There is good documentation on how to write/format patches at:
https://www.openembedded.org/wiki/Commit_Patch_Message_Guidelines
Where to Send Patches
As Poky is an integration repository (built using a tool called combo-layer), patches against the various components should be sent to their respective upstreams:
OpenEmbedded-Core (files in meta/, meta-selftest/, meta-skeleton/, scripts/):
- Git repository: https://git.openembedded.org/openembedded-core/
- Mailing list: openembedded-core@lists.openembedded.org
BitBake (files in bitbake/):
- Git repository: https://git.openembedded.org/bitbake/
- Mailing list: bitbake-devel@lists.openembedded.org
Documentation (files in documentation/):
- Git repository: https://git.yoctoproject.org/cgit/cgit.cgi/yocto-docs/
- Mailing list: docs@lists.yoctoproject.org
meta-yocto (files in meta-poky/, meta-yocto-bsp/):
- Git repository: https://git.yoctoproject.org/cgit/cgit.cgi/meta-yocto
- Mailing list: poky@lists.yoctoproject.org
If in doubt, check the openembedded-core git repository for the content you intend to modify as most files are from there unless clearly one of the above categories. Before sending, be sure the patches apply cleanly to the current git repository branch in question.