kmax 4.5.2

Tools for working with symbolic constraints from Kbuild Makefile.

• The kmax tool suite
  • Getting started
    • Installing the kmax tool suite
    • Kicking the tires
  • Using klocalizer --repair on patches
  • Using koverage
  • Using kismet
  • Additional documentation
  • Bugs found
  • Credits

The kmax tool suite

Getting started

Installing the kmax tool suite

Install the requiste python tools (the kmax tool suite currently depends on python 3.8 or later), setup a python virtual environment (recommended), and finally install the tools from pip.

sudo apt install -y python3 python3-pip python3-venv
python3 -m venv ~/env_kmax/
source ~/env_kmax/bin/activate
pip3 install kmax

Instructions to install from source can be found in the advanced documentation.

Kicking the tires

Install dependencies for compiling Linux source, then download and enter the Linux source:

sudo apt install -y flex bison bc libssl-dev libelf-dev
cd ~/
wget https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.16.tar.xz
tar -xvf linux-5.16.tar.xz
cd ~/linux-5.16/

Run klocalizer --repair to modify allnoconfig so that builds a given compilation unit:

make ARCH=x86_64 allnoconfig
klocalizer --repair .config -o allnoconfig_repaired --include drivers/usb/storage/alauda.o
KCONFIG_CONFIG=allnoconfig_repaired make ARCH=x86_64 olddefconfig clean drivers/usb/storage/alauda.o

You should see CC drivers/usb/storage/alauda.o at the end of the build.

Using klocalizer --repair on patches

This tool will automatically "fix" your .config file so that it builds the lines from a given patchfile (or any specific files or file:line pairs). To use it, first install SuperC, which klocalizer depends on for finding#ifdef constraints:

sudo apt-get install -y libz3-java libjson-java sat4j unzip flex bison bc libssl-dev libelf-dev xz-utils lftp
wget -O - https://raw.githubusercontent.com/appleseedlab/superc/master/scripts/install.sh | bash
export COMPILER_INSTALL_PATH=$HOME/0day
export CLASSPATH=/usr/share/java/org.sat4j.core.jar:/usr/share/java/json-lib.jar:${HOME}/.local/share/superc/z3-4.8.12-x64-glibc-2.31/bin/com.microsoft.z3.jar:${HOME}/.local/share/superc/JavaBDD/javabdd-1.0b2.jar:${HOME}/.local/share/superc/xtc.jar:${HOME}/.local/share/superc/superc.jar:${CLASSPATH}
export PATH=${HOME}/.local/bin/:${PATH}

Too see it in action, start with a clone of the linux repository and create a patch file:

cd ~/
git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
cd ~/linux/
git checkout 6fc88c354f3af
git show > 6fc88c354f3af.diff

Now try using repair to update allnoconfig, which doesn't build all lines from the patch. After repair, the resulting configuration file builds the lines affected by the patch. The last command builds the files affected by the patch, which would have failed with an unrepaired allnoconfig.

make ARCH=x86_64 allnoconfig
klocalizer --repair .config -a x86_64 --include-mutex 6fc88c354f3af.diff
KCONFIG_CONFIG=0-x86_64.config make ARCH=x86_64 olddefconfig clean kernel/bpf/cgroup.o net/ipv4/af_inet.o net/ipv4/udp.o net/ipv6/af_inet6.o net/ipv6/udp.o
koverage --config 0-x86_64.config --arch x86_64 --check-patch 6fc88c354f3af.diff -o coverage_results.json
cat coverage_results.json

When using --include-mutex, the generated configuration files are exported as NUM-ARCH.config, since several configuration files may be needed when patches contain mutually-exclusive lines.

Using klocalizer --save-dimacs and klocalizer --save-smt

This tool extracts a DIMACS or a SMT formula. Therefore, execute the following commands in the root directory of your Linux kernel:

klocalizer -a x86_64 --save-dimacs <Path>
klocalizer -a x86_64 --save-smt <Path>

Note that <Path> should be replaced by the absolute path to the file, the formulae should be written to. If you intend to use a Docker container, feel free to use the Dockerfile provided in Advanced Usage.

Using koverage

koverage checks whether a Linux configuration file includes a set of source file:line pairs for compilation. This following checks whether lines 256 and 261 of kernel/fork.c are included for compilation by Linux v5.16 allyesconfig.

cd ~/linux-5.16/
make.cross ARCH=x86_64 allyesconfig
koverage --config .config --arch x86_64 --check kernel/fork.c:[259,261] -o coverage_results.json
make allnoconfig; klocalizer -v --repair .config --include kernel/fork.c:[259]; rm -rf koverage_files/; koverage -v -a x86_64 --config .config --check kernel/fork.c:[259] -o coverage.out

The coverage results are in coverage_results.json, which indicate that line 259 is included while 261 is excluded by allyesconfig, because the lines are under mutually-exclusive #ifdef branches.

Use --check-patch file.patch to check coverage of all source lines affected by a given patch.

Using kismet

This tool will check for unmet dependency bugs in Kconfig specifications due to reverse dependencies overriding direct dependencies.

Run kismet on the root of the Linux source tree.

kismet --linux-ksrc="${HOME}/linux-5.16/" -a=x86_64

Once finished (it can take about an hour on a commodity desktop), kismet will produce three outputs:

1. A summary of the results in kismet_summary_x86_64.txt
2. A list of results for each select construct in kismet_summary_x86_64.csv (UNMET_ALARM denotes the buggy ones)
3. A list of .config files meant to exercise each bug in kismet-test-cases/

Technical details can be found in in the kismet documentation and the publication on kclause and kismet. The experiment replication script can be used to run kismet on all architectures' Kconfig specifications.

Additional documentation

Advanced Usage

Bugs found

Bugs Found by our tools

Credits

The main developers of this project have been Paul Gazzillo (kextract, kclause, kmax, klocalizer), Necip Yildiran (kismet, krepair, koverage), Jeho Oh (kclause), and Julian Braha (koverage). Julia Lawall has posed new applications and provided invaluable advice, feedback, and support. Thanks to all the users who have contributed code and issues. Special thanks to the Intel 0-day team for working to include kismet into the kernel test robot and for their valuable feedback. This work is funded in part by the National Science Foundation under awards CCF-1840934 and CCF-1941816.