"linking with arm-linux-gnueabihf-gcc failed" when cross-compiling a Rust application from macOS to a Raspberry Pi 2

Question

I want to cross-compile my Rust application on macOS to a Raspberry Pi 2. I searched a lot, but did not find a working solution. The last solution I tried was following this answer, but I couldn't get it to work.

• macOS version: 10.13.5 (High Sierra)
• rustup version: 1.11.0
• cargo version: 1.26.0

What I did:

• I cloned raspberrypi/tools
• Installed arm-unknown-linux-gnueabihf and armv7-unknown-linux-gnueabihf toolchains via rustup

• Created .cargo/config file in the root of my project with following content

  [target.armv-unknown-linux-gnueabihf]
  linker = "/Users/user/Documents/Programming/RustProjects/hello-pi/../../Utils/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/arm-linux-gnueabihf-gcc"
  

• Then I run cargo build --target=arm-unknown-linux-gnueabihf

I get the following error:

linking with /Users/user/Documents/Programming/RustProjects/hello-pi/../../Utils/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/arm-linux-gnueabihf-gcc failed: exit code: 126
....
cannot execute binary file

It seems that I cannot run the ...gcc binary on my macOS machine. What would be the right way to cross-compile my Rust application from macOS to the ARM architecture for a Raspberry Pi 2?

Answer 1

rust-std library relies on glibc for things like syscalls and other low-level stuff, in order to cross-compile a Rust binary, one needs the appropriate C toolchain to be present as well. And this is where crosstool-NG comes into play.

crosstool-NG is in the toolchain building business. You’re going to use it to build yourself a toolchain for linking against ARMv7-compatible glibc, which will in turn allow you to successfully build your Rust binary for the Pi.

• Clone the repo to a good location and bootstrap it:

cd /Users/USER
git clone https://github.com/crosstool-ng/crosstool-ng
cd crosstool-ng
./bootstrap

• Configure the installation and run it. To set where the tool goes on install, run:

./configure --prefix=$PWD
make
make install
export PATH="${PATH}:${PWD}/bin"

If all things went as expected, you should be able to run ct-ng version and verify the tool’s ready to go.

• Configure the tool to build your ARMv7 toolchain. Luckily, crosstool-NG comes with some preset configurations, namely armv7-rpi2-linux-gnueabihf. Run:

ct-ng armv7-rpi2-linux-gnueabihf

There should be some output indicating that it’s now configured for armv7-rpi2-linux-gnueabihf. You just need to tell ct-ng where the toolchain ought to go:

mkdir /Users/USER/ct-ng-toolchains
cd /Users/USER/ct-ng-toolchains
ct-ng menuconfig

It can be overwhelming, as there are a ton of options, but stick to the Paths and misc options ---> menu option. Highlight it and hit Enter.

Under *** crosstool-NG behavior ***, scroll down until you see this long string: (${CT_PREFIX:-${HOME}/x-tools}/${CT_HOST:+HOST-${CT_HOST}/}${CT_TARGET}) Prefix directory - Hit Enter, delete the contents, and replace it with /Users/USER/ct-ng-toolchains. - When you’re finished, hit Enter to confirm, scroll over and save, and then exit the configurator.

• Build your toolchain (this may take half an hour):

ct-ng build

• If it worked successfully, You should see a great many binaries now in /Users/USER/ct-ng-toolchains/armv7-rpi2-linux-gnueabihf/bin, namely armv7-rpi2-linux-gnueabihf-gcc.

• For cargo to build using your new cross-compiler, you must:

  1. Add the bin folder listed above to your PATH:

export PATH="${PATH}:/Users/USER/ct-ng-toolchains/armv7-rpi2-linux-gnueabihf/bin"

2. Update (or create) your global /Users/USER/.cargo/config file with (you can avoid this and use it in local .cargo/config):

[target.armv7-unknown-linux-gnueabihf]
linker = "armv7-rpi2-linux-gnueabihf-gcc"

3.Return to your Rust project and rerun cargo build:

cd /Users/USER/rust/hello
cargo build --target=armv7-unknown-linux-gnueabihf

4. The output should be something similar to:

   Compiling hello v0.1.0 (file:///Users/USER/rust/hello)
    Finished dev [unoptimized + debuginfo] target(s) in 0.85 secs

5. SCP your file over to the RPi and run the binary remotely:

scp target/armv7-unknown-linux-gnueabihf/debug/hello [email protected]:
ssh [email protected] 'chmod +x ~/hello && ~/hello'
Hello, world!

Credit goes to Kappel Codes I tried to summarize it here, as I found this question hours before I get that article :)