This guide builds on the guide from Amarit Rathie, which has been an indispensible resource in getting me started with cross-compilation at all. Mine has been updated for the latest versions of macOS at the time, and I’ve tried it on an M2 Mac – here, I’m the steps (and workarounds) required to get it to work for me – explanations are kept short, and I encourage you to reference the original blogpost to get a better understanding of what’s going on.

Adding the compilation target

I’m on a 32-Bit Raspberry Pi 3, so I did the following:

rustup target add armv7-unknown-linux-musleabihf

I assume that a 64-bit Raspberry Pi needs a different cross-compilation setup. If you have info on this, drop me a line, and I’ll happily edit it here!

Setup linker

brew install arm-linux-gnueabihf-binutils

Setup musl cross compilation toolchain

brew install FiloSottile/musl-cross/musl-cross
brew reinstall musl-cross --without-x86_64 --without-aarch64 --with-arm-hf

(This is a workaround for the brew issue invalid option: --without-x86_64)

Using a cross-compilation toolchain fixes issues like error occurred: Failed to find tool. Is `arm-linux-musleabihf-gcc` installed?, which I encountered on my first attempts.

Setup linker

Put this in your .cargo/config:

linker = "arm-linux-gnueabihf-ld"
ar = "arm-linux-gnueabihf-ar" # optional

As Amirit mentions in his guide, you can either do this for the current project (the option I went for), or alternatively specify it globally in ~/.cargo/config.

Build your app

cargo build --target armv7-unknown-linux-musleabihf

OpenSSL issues

Encountered issue with OpenSSL: Could not find directory of OpenSSL installation, and this `-sys` crate cannot proceed without this knowledge. I don’t have a fix for it, but there is a workaround: use a different SSL implementation. reqwest, for example, supports rustls out of the box. Remember to turn off default-features, otherwise this won’t work!

reqwest = { version = "0.11.23", features = ["json", "rustls"], default-features = false }

Enjoy building some oxidized binaries for your Raspberry!