# OpenJDK RISC-V Port Cross-compiling Guide

## Prerequisites

This guide is based on `adoptopenjdk/centos6_build_image`, which requires docker installed on your machine.

- docker
- [adoptopenjdk/centos6_build_image](https://hub.docker.com/r/adoptopenjdk/centos6_build_image)

Get the latest centos6 build image:

```
$ docker pull adoptopenjdk/centos6_build_image:latest
```

## Build OpenJDK RISC-V Port From Source

Run `adoptopenjdk/centos6_build_image`:

```
$ docker run -it --rm adoptopenjdk/centos6_build_image
```

### Get Source

OpenJDK RISC-V port is upstreamed, you can get source from [openjdk/jdk](https://github.com/openjdk/jdk):

```
$ git clone https://github.com/openjdk/jdk.git
```

### Configure & Build

Cross-compiling setup:

```
# add riscv toolchain to PATH and LD_LIBRARY_PATH
$ export RISCV64=/opt/riscv_toolchain_linux
$ export LD_LIBRARY_PATH=$RISCV64/lib64:/usr/local/gcc/lib64:/usr/local/gcc/lib
$ export PATH="$RISCV64/bin:$PATH"
$ export CC=$RISCV64/bin/riscv64-unknown-linux-gnu-gcc
$ export CXX=$RISCV64/bin/riscv64-unknown-linux-gnu-g++

# configure and build
$ bash configure                                \
    --openjdk-target=riscv64-unknown-linux-gnu  \
    --with-sysroot=/opt/fedora28_riscv_root     \
    --with-boot-jdk=/usr/lib/jvm/jdk-17         \
    BUILD_CC=/usr/local/gcc/bin/gcc-7.5         \
    BUILD_CXX=/usr/local/gcc/bin/g++-7.5
$ make images
```

## Version Test

### Build QEMU from source

Get source code:

```
git clone https://github.com/qemu/qemu.git
```

Configure and build:

```
cd qemu && mkdir build && cd build
../configure --prefix=/path/to/install/qemu --target-list=riscv64-linux-user,riscv64-softmmu
make -j && make install
```

### QEMU User Mode

When running version test with QEMU user mode, you need to set the library path with `-L` option:

```
$ qemu-riscv64 -L /path/to/sysroot /path/to/openjdk-riscv/bin/java -version
```

For example:

```
$ qemu-riscv64 -L /opt/fedora28_riscv_root jdk/bin/java -version
```

### QMEU System Mode

It is easier to run in QEMU system mode, following command would be enough:

```
$ /path/to/openjdk-riscv/bin/java -version
```

For example:

```
$ jdk/bin/java -version
```

The output should be:

```
openjdk version "19-internal" 2022-09-20
OpenJDK Runtime Environment (build 19-internal+0-adhoc..riscv-port)
OpenJDK 64-Bit Server VM (build 19-internal+0-adhoc..riscv-port, mixed mode, sharing)
```