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clang-kernel-build

Steps to build the Linux kernel using Clang

  1. Start with an empty dir

    git clone https://github.com/ramosian-glider/clang-kernel-build.git
    cd clang-kernel-build
    export WORLD=`pwd`
    
  2. Install Clang from Chromium:

    cd $WORLD
    # Instruction taken from http://llvm.org/docs/LibFuzzer.html
    mkdir TMP_CLANG
    cd TMP_CLANG
    git clone https://chromium.googlesource.com/chromium/src/tools/clang
    cd ..
    TMP_CLANG/clang/scripts/update.py
    

(To update Clang later on, do (cd TMP_CLANG/clang ; git pull) and run update.py again.)

  1. Clone the Linux source tree

    cd $WORLD
    git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
    cd linux-stable
    git reset --hard v5.2-rc4
    
  2. Configure and build the kernel

    cd $WORLD
    export CLANG_PATH=`pwd`/third_party/llvm-build/Release+Asserts/bin/
    cd linux-stable
    make CC=$CLANG_PATH/clang defconfig
    make CC=$CLANG_PATH/clang -j64 2>&1 | tee build.log
    
  3. Set up the VM:

    cd $WORLD
    wget https://raw.githubusercontent.com/google/sanitizers/master/address-sanitizer/kernel_buildbot/create_os_image.sh
    # create_os_image.sh requires sudo
    sh create_os_image.sh
    
  4. Run the VM

    cd $WORLD
    ./run_qemu.sh
    # in a separate console:
    ssh -i ssh/id_rsa -p 10023 root@localhost
    

Debugging

```
# Start the VM before running GDB
cd $WORLD
gdb -x gdb.script
(gdb) br dump_stack
```

Hacking

```
# Perform these steps instead of Step 4 above.
cd $WORLD/linux-stable
make CC=$CLANG_PATH/clang defconfig
make CC=`pwd`/../clang_wrapper.py 2>&1 | tee build.log
```

The handy clang_wrapper.py lets you add arguments to Clang invocation, measure compilation times or fall back to GCC for certain files.

Also, get yourself a log symbolizer: https://raw.githubusercontent.com/google/sanitizers/master/address-sanitizer/tools/kasan_symbolize.py