Running Linux on VDK

⚠️ There is no guarantee that this guide will be applicable for newer versions of a Linux kernel or a toolchain.

Preface

This guide is tested on VDK HS38x4 2020.09. VDK itself requires nSIM Pro license. ARC GNU toolchain 2017.09 based on uClibc-ng library is used for building a Linux kernel. Ubuntu 18.04 is used as a host system.

Prerequisites

Install packages for Ubuntu 18.04:

$ sudo apt install xterm libgl1-mesa-dri libsdl1.2debian

Build Linux Kernel and Filesystem Image

Clone the latest Buildroot:

$ git clone https://git.busybox.net/buildroot
$ cd buildroot

Filesystem images must not be linked against Linux kernel for running on VDK. Also, vdk_hs38_smp configuration file must be used for the Linux kernel. Create a vdk_defconfig configuration file in configs directory with a correct configuration:

BR2_arcle=y
BR2_archs38=y
BR2_TOOLCHAIN_EXTERNAL=y
BR2_TOOLCHAIN_EXTERNAL_CUSTOM=y
BR2_TOOLCHAIN_EXTERNAL_DOWNLOAD=y
BR2_TOOLCHAIN_EXTERNAL_URL="https://github.com/foss-for-synopsys-dwc-arc-processors/toolchain/releases/download/arc-2017.09-release/arc_gnu_2017.09_prebuilt_uclibc_le_archs_linux_install.tar.gz"
BR2_TOOLCHAIN_EXTERNAL_GCC_7=y
BR2_TOOLCHAIN_EXTERNAL_HEADERS_4_12=y
BR2_TOOLCHAIN_EXTERNAL_LOCALE=y
BR2_TOOLCHAIN_EXTERNAL_HAS_SSP=y
BR2_TOOLCHAIN_EXTERNAL_CXX=y
BR2_LINUX_KERNEL=y
BR2_LINUX_KERNEL_CUSTOM_VERSION=y
BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.9"
BR2_LINUX_KERNEL_DEFCONFIG="vdk_hs38_smp"
BR2_LINUX_KERNEL_VMLINUX=y
BR2_TARGET_ROOTFS_EXT2=y

Build images:

$ make vdk_defconfig
$ make

Linux kernel and filesystem images reside in output/images now:

$ ls output/images/
rootfs.ext2  rootfs.tar  vmlinux

Running Linux on VDK

ARC HS VDK already includes Linux kernel image and root file system image. Save old images and replace them with your newly generated files:

$ cd <VDK-directory>/skins/ARC-Linux
$ mv rootfs.ARCv2.ext2{,.orig}
$ cp <Buildroot-source-tree>/output/images/rootfs.ext2 rootfs.ARCv2.ext2
$ mv ARCv2/vmlinux_smp-noSD{,.orig}
$ cp <Buildroot-source-tree>/output/images/vmlinux ARCv2/vmlinux_smp-noSD

Run a simulator:

$ <VDK-directory>/skins/ARC-Linux/start_interactive.tcl

Configuring Network

Before running VDK if you wish to have a working networking connection on Linux for ARC system it is required to configure VDK VHub application. By default this application will pass all Ethernet packets to the VDK Ethernet model, however on busy networks that can be too much to handle in a model, therefore it is highly recommended to configure destination address filtering. Modify VirtualAndRealWorldIO/VHub/vhub.conf: set DestMACFilterEnable to true, and append some random valid MAC address to the list of DestMACFilter, or use one of the MAC address examples in the list. This guide will use D8:D3:85:CF:D5:CE - this address is already in the list. Note that is has been observed that it is not possible to assign some addresses to Ethernet device model in VDK, instead of success there is an error “Cannot assign requested address”.

Note, that due to the way how VHub application works, it is impossible to connect to the Ethernet model from the host on which it runs on and vice versa. Therefore to use networking in target it is required to either have another host and communicate with it.

Run VHub application as root:

# <VDK-directory>/VirtualAndRealWorldIO/VHub/vhub -f VirtualAndRealWorldIO/VHub/vhub.conf

In another console launch VDK:

$ <VDK-directory>/skins/ARC-Linux/start_interactive.tcl

After VDK will load, start simulation. After Linux kernel will boot, login into system via UART console: login root, no password. By default networking is switched off. Enable eth0 device, configure it is use MAC from address configured in VHub:

# ifconfig eth0 hw ether d8:d3:85:cf:d5:ce
# ifconfig eth0 up

Linux kernel will emit errors about failed PTP initialization - those are expected. Assign IP address to the target system. This example uses DHCP:

# udhcpc eth0

Now it is possible to mount some NFS share and run applications from it:

# mount -t nfs public-nfs:/home/arc_user/pub /mnt
# /mnt/hello_world