Cross Compiling

Prerequisites

You need three things on the host system:

  1. The Bro source tree.
  2. A cross-compilation toolchain, such as one built via crosstool-NG.
  3. Pre-built Bro dependencies from the target system. This usually includes libpcap, zlib, OpenSSL, and Python development headers and libraries.

Configuration and Compiling

You first need to compile a few build tools native to the host system for use during the later cross-compile build. In the root of your Bro source tree:

./configure --builddir=../bro-buildtools
( cd ../bro-buildtools && make binpac bifcl )

Next configure Bro to use your cross-compilation toolchain:

./configure --toolchain=/home/jon/x-tools/RaspberryPi-toolchain.cmake --with-binpac=$(pwd)/../bro-buildtools/aux/binpac/src/binpac --with-bifcl=$(pwd)/../bro-buildtools/src/bifcl

Here, the toolchain file a CMake toolchain file. It might look something the following (using a Raspberry Pi as target system):

# Operating System on which CMake is targeting.
set(CMAKE_SYSTEM_NAME Linux)

# The CMAKE_STAGING_PREFIX option may not work.
# Given that Bro is configured:
#
#   `./configure --prefix=<dir>`
#
# The options are:
#
#   (1) `make install` and then copy over the --prefix dir from host to
#       target system.
#
#   (2) `DESTDIR=<staging_dir> make install` and then copy over the
#       contents of that staging directory.

set(toolchain /home/jon/x-tools/arm-rpi-linux-gnueabihf)
set(CMAKE_C_COMPILER   ${toolchain}/bin/arm-rpi-linux-gnueabihf-gcc)
set(CMAKE_CXX_COMPILER ${toolchain}/bin/arm-rpi-linux-gnueabihf-g++)

# The cross-compiler/linker will use these paths to locate dependencies.
set(CMAKE_FIND_ROOT_PATH
    /home/jon/x-tools/bro-rpi-deps
    ${toolchain}/arm-rpi-linux-gnueabihf/sysroot
)

set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

If that configuration succeeds you are ready to build:

make

And if that works, install on your host system:

make install

From there, you can copy/move the files from the installation prefix on the host system to the target system and start running Bro as usual.