Depending on what ISA you're using with gem5 the instructions for compiling a Linux kernel differ slightly. Ultimately, we'd like to have a single unified way to compile all these kernels, but it will take some work to happen. If you'd like to help, please let us know.
Currently we have a patch queue for Alpha that can be applied on top of a linux mercurial repository. This patch queue adds various debugging, performance, introspection capabilities and increases the number of simulated processors the Alpha implementation in gem5 can support from 4 to 64. To compile a new kernel for Alpha follow the directions below:
# First clone a copy of the linux repository hg clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6.git linux-2.6 cd linux-2.6 # Go to the .hg directory cd .hg #Get a copy of the patches repository hg clone http://repo.gem5.org/linux-patches patches # Go back to the linux directory cd .. #Update the linux repository to a known working version hg update v2.6.27 # Select the patches for 2.6.27 hg qselect 2.6.27 # Apply the patches to the repository hg qpush -a # Copy the default config file to .config cp .config.m5 .config # Build the kernel make ARCH=alpha CROSS_COMPILE=/path/to/alpha/compiler/alpha-unknown-linux-gnu- vmlinux -j 4
I few minutes later a kernel will be compiled. You can use a newer version of m5, however you'll likely need to modify the config file and some of the patches slightly for it to work.
See ARM Linux Kernel.
x86 doesn't currently have a patch queue, but a generic kernel works well since the normal code already has functions that wait for interrupts in idle loops. Some of the debugging functionality, such as m5dprintk can be trivially added if you need to by just using the patch from the alpha linux-patches repository above.
# To compile a kernel for x86, first get the kernel source. Here again we use mercurial because that is what we use for gem5 # However, you could get the code from kernel.org in a bzip format hg clone http://www.kernel.org/hg/linux-2.6 # Change directory to the newly cloned directory cd linux-2.6 # Update to the version you're interested in; 126.96.36.199 in this case because that is what the config file we've got is for hg update v188.8.131.52 # Grab the config file on the download page: wget http://www.m5sim.org/dist/current/x86/config-x86.tar.bz2 tar jxvf config-x86.tar.bz2 cp configs/linux-184.108.40.206 .config # Compile the kernel, assuming you're building on an x86 host make vmlinux -j 4