Debian Toolchain installation

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Debian toolchain installation for out of Debian builds

Installing the toolchain

To install the toolchain, please go through the following steps of the Debian Build Release guide:

1. Setup Development Environment
2. Installing required packages
3. Download Debian archive
4. Deploy/Fetch the sources and components

You will have a development environment from this point, including the toolchain and the packages ready to be used.

The GNU Linux toolchain gcc-linaro-6.3.1-2017.05-x86_64_aarch64-linux-gnu can be found at ~/debian_imx8mq-var-dart_debian_bullseye/toolchain.

Note: Alternatively, you can download the toolchain directly from the Linaro toolchain binaries archive. Anyway, If you're considering downloading the toolchain directly, please still follow the steps 1 and 2.

Create a sysroot

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. Accordingly, to create the sysroot, we would first need the full Debian rootfs. 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, we can start creating 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 file system located on the host, please see here for more information
• symlinks can convert absolute paths to relative ones within a file system, please see here 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.

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.