Cross-compilig Unikraft

Cross-compiling AArch64 apps#

The toolchain that should be used for AArch64 is aarch64-none-elf, to be installed from the official Arm development site.

Similar with the command we'll present for cross-compiling with clang, we build the app using

$ make -j $(nproc) CROSS_COMPILE=~/toolchains/gcc-arm-11.2-2022.02-x86_64-aarch64-none-elf/bin/aarch64-none-elf-

Cross-compiling Unikraft with Clang#

As clang becomes more and more used in the industry, we also provide a series of steps in order to compile your application with it. Besides coming up with cool sanitizers (SafeStack, ShadowStack and more), clang becomes a very interesting alternative to gcc when it comes to speed and memory¹, so why not give it a try?!

Firstly, we must consider what architecture we are working on, because the steps differ quite a bit.

Clang on x86#

Configure your application as you would usually do, then build it using:

$ make CC=clang

Clang on AArch64#

There are two ways of cross-compiling your app based off the toolchain you'll choose; there's either aarch64-linux-gnu or aarch64-none-linux-gnu. The first one can be installed via your default package manager (the gcc-aarch64-linux-gnu package on Ubuntu), while the second one should be fetched from the official Arm development site.

To configure your app keep your regular configuartions and dissable all the erratums from the Architecture Selection.

• If you choose to use aarch64-linux-gnu, build your application with:

$ make -j $(ncpus) CC=clang

• If you choose to use aarch64-none-linux-gnu, build your application with:

$ make -j $(ncpus) CROSS_COMPILE=~/toolchains/gcc-arm-11.2-2022.02-x86_64-aarch64-none-linux-gnu/bin/aarch64-none-linux-gnu- CC=clang

The actual right way of building apps on AArch64 is by cross-compiling with aarch64-none-elf, as the other toolchains expect glibc to be used, while that's not the case for unikraft.

However, aarch64-none-elf clashes with our expectations regarding the emutls and becomes unusable together with clang.