Show HN: Compile for Arm at native speeds in an emulated system

Prebuilt images available on Docker Hub

https://hub.docker.com/repository/docker/valkmit/aws-graviton2-on-intel

What is this?

An Arm filesystem based off an AWS Graviton 2 system. All binaries are emulated under Qemu, EXCEPT for a custom toolchain built with Buildroot. The toolchain is run natively, allowing for up to 20x faster compile times than when emulated.

# file $(which bash)
/usr/bin/bash: ELF 64-bit LSB executable, ARM aarch64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 3.7.0, BuildID[sha1]=03b374959d488851f8b6ef51a6a16e55eaedea98, stripped

# file $(realpath $(which aarch64-linux-gcc))
/x86_64/host/bin/toolchain-wrapper: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 3.2.0, BuildID[sha1]=9c88d4609953b73d518a95e44ebc93d642a8174e, stripped

Usage

If you wish to build the Docker image from source, you must run ./build.sh. At a minimum, you must provide the rootfs as a .tar.gz with -r. The script will download buildroot if it is not provided with -b. For a prebuilt image, please visit the corresponding Docker hub page (link provided above).

The only requirement to build is Docker - both Qemu and the toolchain are built in Docker containers based on Debian 10.

All of the native cross compile tools are available prefixed with aarch64-linux. For example, aarch64-linux-gcc, or aarch64-linux-g++. To observe how the toolchain is configured, you may view buildroot-graviton2-config.

Spin up an image quickly to play around with the compilers:

docker run -it --rm valkmit/aws-graviton2-on-intel

Justification

When compiling for a target architecture different from the host architecture, developers have roughly two options

1. Set up a cross toolchain, which has fast performance, but makes it very difficult to automatically satisfy complex dependencies. For a sufficiently large project, this could mean compiling dozens of projects by hand using the newly built cross toolchain

2. Emulate the target system, which makes dependency satisfaction easier, since a native package manager can be used, but slows down compile times - the compiler has to be emulated, too!

This project is designed to give developers the best of both worlds - the ease of using the target system's package manager (in this case, Yum configured with all of Amazon's aarch64 repos) - and the speed of native compilers.

Long story short, a native cross-compiler is transplanted onto the Gravon2 Arm filesystem. This project could probably be extended for other systems, too.

Isn't a Docker container configured with binfmt-misc superior?

Normally, yes. However, binfmt-misc currently doesn't have namespace support (though this is in the pipeline!) This means that if you choose to go the binfmt-misc route, you must run a privileged container. This project does not require a privileged Docker container.

The lack of requirement of privileged container means that you may use this on public build systems that do not have Arm support, and expect much better performance.

Credits

Lots of back and forth with gh:MelloJello

from Hacker News https://ift.tt/3jv9tPW