Linux boot-exit image

This document provides instructions to create the “boot-exit” image, the Linux kernel binaries, and also points to the gem5 configuration files needed to run the boot. The boot-exit disk image is based on Ubuntu 18.04 and has its .bashrc file modified in such a way that the guest OS terminates the simulation (using the m5 exit instruction) as soon as the system boots.

We assume the following directory structure while following the instructions in this README file:

  |___ gem5/                                   # gem5 source code
  |___ disk-image/
  |      |___ shared/                          # Auxiliary files needed for disk creation
  |      |___ boot-exit/
  |            |___ boot-exit-image/           # Will be created once the disk is generated
  |            |      |___ boot-exit           # The generated disk image
  |            |___ boot-exit.json             # The Packer script
  |            |___                    # Exits the simulated guest upon booting
  |            |___       # Moves to guest's .bashrc
  |___ configs
  |      |___ system                           # gem5 system config files
  |      |___                      # gem5 run script
  |___ linux-configs                           # Folder with Linux kernel configuration files
  |___ linux                                   # Linux source will be downloaded in this folder
  |___                               # This README file

Disk Image

Assuming that you are in the src/boot-exit/ directory (the directory containing this README), first build m5 (which is needed to create the disk image):

git clone
cd gem5/util/m5
scons build/x86/out/m5


cd disk-image
# if packer (tool to build the disk) is not already installed

# validate the packer script
./packer validate boot-exit/boot-exit.json
# build the disk image
./packer build boot-exit/boot-exit.json

If you see errors or warnings from packer validate you can modify the file disk-image/boot-exit/boot-exit.json to update the file. Specifically, you may see the following error.

Error: Failed to prepare build: "qemu"

1 error(s) occurred:

* Bad source '../gem5/util/m5/build/x86/out/m5': stat
../gem5/util/m5/build/x86/out/m5: no such file or directory

In this case, the gem5 directory is in a different location than when this script was written. You can update the following line in the boot-exit.json file.

         "destination": "/home/gem5/",
-        "source": "../gem5/util/m5/build/x86/out/m5",
+        "source": "<your path to gem5>/util/m5/build/x86/out/m5",
         "type": "file"

Once this process succeeds, the disk image can be found on boot-exit/boot-exit-image/boot-exit. A disk image already created following the above instructions can be found, gzipped, here.

gem5 Run Scripts

gem5 scripts which configure the system and run simulation are available in configs-boot-tests/. The main script expects following arguments:

kernel: path to the Linux kernel.

disk: path to the disk image.

cpu_type: cpu model (kvm, atomic, simple, o3).

mem_sys: memory system (classic, MI_example, MESI_Two_Level, MOESI_CMP_directory).

num_cpus: number of cpu cores.

boot_type: Linux kernel boot type (init, systemd).

An example use of this script is the following:

gem5/build/X86/gem5.opt configs/ [path to the Linux kernel] [path to the disk image] kvm classic 4 init

Linux Kernels

Boot tests use following five LTS (long term support) releases of the Linux kernel:

  • 4.4.186
  • 4.9.186
  • 4.14.134
  • 4.19.83
  • 5.4.49

To compile the Linux binaries, follow these instructions (assuming that you are in src/boot-exit/ directory):

git clone
cd linux
# replace version with any of the above listed version numbers
git checkout v[version]
# copy the appropriate Linux kernel configuration file from linux-configs/
cp ../linux-configs/config.[version] .config
make -j8;

The compiled Linux binary will be named as vmlinux.

Note: The above instructions are tested with gcc 7.5.0 and the compiled Linux binaries can be downloaded from the following links:

Working Status

Working status of these tests for gem5-20 can be found here.