Debian Toolchain installation

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Debian toolchain for cross-compilation

Prerequisites

Please follow steps 2 & 4 of the Build Debian from source code guide, to setup a Debian build environment.

Obtain the toolchain

The toolchain can be downloaded by running the following:

$ cd ~/debian_imx8mq-var-dart_debian_bullseye
$ MACHINE=imx8mq-var-dart ./var_make_debian.sh -c deploy

This will download the toolchain gcc-linaro-6.3.1-2017.05-x86_64_aarch64-linux-gnu (or a newer version), which can be found at ~/debian_imx8mq-var-dart_debian_bullseye/toolchain.

Create a sysroot for user space cross-compilation

A sysroot is basically a scaled-downed version of the target file system to be used on the host for cross-compilation of user space applications.

In the following we will show how to create the sysroot using a script, pre-shipped with the Debian archive, or manually. In any case, we would need a full Debian rootfs first, please refer to Setup and build Debian to learn how to build it. Once the rootfs have been built, it should be present at ~/debian_imx8mq-var-dart_debian_bullseye/rootfs. From this point, follow one of the upcoming sections.

Notes:

• The Debian build script uses debootstrap to create a minimal Debian Bullseye system and adds the BSP support. Please consider installing extra (dev-)packages to your Debian file system as per your needs.
  To do this, follow the Adding Debian packages guide to learn how to add packages to the rootfs.
• Keeping the sysroot in sync with the rootfs of the target is recommended to avoid misalignments. Whenever a change has been made to the rootfs, please consider creating a new sysroot as described.

Use the script to create the sysroot

The script to create the sysroot is located at ~/debian_imx8mq-var-dart_debian_bullseye/variscite/scripts:

$ cd ~/debian_imx8mq-var-dart_debian_bullseye
$ sudo MACHINE=imx8m-var-dart ./variscite/scripts/make-sysroot.sh

Manual step-by-step to create the sysroot

First, create a temporary copy of the origin rootfs:

$ cd ~/debian_imx8mq-var-dart_debian_bullseye
$ mkdir -p tmp/rootfs
$ sudo cp -ar rootfs/. tmp/rootfs

Next, we need to convert all absolute links to relative ones. The following approach will use the tools chroot and symlinks.

Notes:

• chroot along with QEMU emulates a target access on the rootfs, please see chroot docs for more information
• symlinks can convert absolute paths to relative ones within a file system, please see symlinks docs for more information

Chroot to the rootfs with the following commands:

$ export ROOTFS_BASE=tmp/rootfs
$ sudo cp variscite/qemu_64bit/qemu-aarch64-static ${ROOTFS_BASE}/usr/bin/qemu-aarch64-static
$ sudo mount -o bind /proc ${ROOTFS_BASE}/proc
$ sudo mount -o bind /dev ${ROOTFS_BASE}/dev
$ sudo mount -o bind /sys ${ROOTFS_BASE}/sys
$ sudo mount -o bind /dev/pts ${ROOTFS_BASE}/dev/pts
$ sudo chroot $ROOTFS_BASE

Once entered, we can now install symlinks and convert the links:

# apt-get install -y symlinks
# symlinks -cr /

and exit:

# exit

Then we need to clean up the mounts (previously needed to chroot):

$ sudo umount ${ROOTFS_BASE}/dev/pts
$ sudo umount ${ROOTFS_BASE}/sys
$ sudo umount ${ROOTFS_BASE}/dev
$ sudo umount ${ROOTFS_BASE}/proc

Finally, create the sysroot target folder:

$ mkdir -p toolchain/sysroot
$ mkdir -p toolchain/sysroot/usr

And copy a minimal required set of the modified origin rootfs to it.
The minimal required set includes:

• /lib: Libraries for programming and packages
• /usr/lib: Libraries for programming and packages
• /usr/include: Directory for standard include files

$ cp -ar tmp/rootfs/lib toolchain/sysroot/
$ cp -ar tmp/rootfs/usr/lib toolchain/sysroot/usr
$ cp -ar tmp/rootfs/usr/include toolchain/sysroot/usr

Note: This guide covers adding the minimal required folders to the sysroot, you can add more per your needs. Doing it, be aware of keeping the original file tree layout.

To clean up, delete the temporary rootfs:

$ sudo rm -rf tmp/rootfs 

The Debian sysroot is now located at ~/debian_imx8mq-var-dart_debian_bullseye/toolchain/sysroot and can be used to cross-compile your user space applications on the host.