riscv64gc-unknown-linux-gnu

Tier: 2 (with Host Tools)

RISC-V targets using the RV64I base instruction set with the G collection of extensions, as well as the C extension.

Target maintainers

Requirements

This target requires:

  • Linux Kernel version 4.20 or later
  • glibc 2.17 or later

Building the target

These targets are distributed through rustup, and otherwise require no special configuration.

If you need to build your own Rust for some reason though, the targets can be enabled in config.toml. For example:

[build]
target = ["riscv64gc-unknown-linux-gnu"]

Building Rust programs

On a RISC-V host, the riscv64gc-unknown-linux-gnu target should be automatically installed and used by default.

On a non-RISC-V host, add the target:

rustup target add riscv64gc-unknown-linux-gnu

Then cross compile crates with:

cargo build --target riscv64gc-unknown-linux-gnu

Testing

There are no special requirements for testing and running the targets. For testing cross builds on the host, please refer to the "Cross-compilation toolchains and C code" section below.

Cross-compilation toolchains and C code

A RISC-V toolchain can be obtained for Windows/Mac/Linux from the riscv-gnu-toolchain repostory. Binaries are available via embecosm, and may also be available from your OS's package manager.

On Ubuntu, a RISC-V toolchain can be installed with:

apt install gcc-riscv64-linux-gnu g++-riscv64-linux-gnu libc6-dev-riscv64-cross

Depending on your system, you may need to configure the target to use the GNU GCC linker. To use it, add the following to your .cargo/config.toml:

[target.riscv64gc-unknown-linux-gnu]
linker = "riscv64-linux-gnu-gcc"

If your riscv64-linux-gnu-* toolchain is not in your PATH you may need to configure additional settings:

[target.riscv64gc-unknown-linux-gnu]
# Adjust the paths to point at your toolchain
cc = "/TOOLCHAIN_PATH/bin/riscv64-linux-gnu-gcc"
cxx = "/TOOLCHAIN_PATH/bin/riscv64-linux-gnu-g++"
ar = "/TOOLCHAIN_PATH/bin/riscv64-linux-gnu-ar"
ranlib = "/TOOLCHAIN_PATH/bin/riscv64-linux-gnu-ranlib"
linker = "/TOOLCHAIN_PATH/bin/riscv64-linux-gnu-gcc"

To test cross compiled binaries on a non-RISCV-V host, you can use qemu. On Ubuntu, a RISC-V emulator can be obtained with:

apt install qemu-system-riscv64

Then, in .cargo/config.toml set the runner:

[target.riscv64gc-unknown-linux-gnu]
runner = "qemu-riscv64-static -L /usr/riscv64-linux-gnu -cpu rv64"

On Mac and Linux, it's also possible to use lima to emulate RISC-V in a similar way to how WSL2 works on Windows:

limactl start template://riscv
limactl shell riscv

Using Docker (with BuildKit) the riscv64/ubuntu image can be used to buiild or run riscv64gc-unknown-linux-gnu binaries.

docker run --platform linux/riscv64 -ti --rm --mount "type=bind,src=$(pwd),dst=/checkout" riscv64/ubuntu bash