Add instructions for how to cross-compile QEMU for RISC-V. The file is named generically because there's no reason not to collect other architectures steps into the same file, especially because several subsections like those for cross-compiling QEMU dependencies using meson and a cross-file could be shared. Additionally, other approaches to creating sysroots, such as with debootstrap, may be documented in this file in the future.
Signed-off-by: Andrew Jones <ajo...@ventanamicro.com> --- docs/devel/cross-compiling.rst | 221 +++++++++++++++++++++++++++++++++ docs/devel/index-build.rst | 1 + 2 files changed, 222 insertions(+) create mode 100644 docs/devel/cross-compiling.rst diff --git a/docs/devel/cross-compiling.rst b/docs/devel/cross-compiling.rst new file mode 100644 index 000000000000..1b988ba54e4c --- /dev/null +++ b/docs/devel/cross-compiling.rst @@ -0,0 +1,221 @@ +.. SPDX-License-Identifier: GPL-2.0-or-later + +==================== +Cross-compiling QEMU +==================== + +Cross-compiling QEMU first requires the preparation of a cross-toolchain +and the cross-compiling of QEMU's dependencies. While the steps will be +similar across architectures, each architecture will have its own specific +recommendations. This document collects architecture-specific procedures +and hints that may be used to cross-compile QEMU, where typically the host +environment is x86. + +RISC-V +====== + +Toolchain +--------- + +Select a root directory for the cross environment +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Export an environment variable pointing to a root directory +for the cross environment. For example, :: + + $ export PREFIX="$HOME/opt/riscv" + +Create a work directory +^^^^^^^^^^^^^^^^^^^^^^^ + +Tools and several components will need to be downloaded and built. Create +a directory for all the work, :: + + $ export WORK_DIR="$HOME/work/xqemu" + $ mkdir -p "$WORK_DIR" + +Select and prepare the toolchain +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Select a toolchain such as [riscv-toolchain]_ and follow its instructions +for building and installing it to ``$PREFIX``, e.g. :: + + $ cd "$WORK_DIR" + $ git clone https://github.com/riscv/riscv-gnu-toolchain + $ cd riscv-gnu-toolchain + $ ./configure --prefix="$PREFIX" + $ make -j$(nproc) linux + +Set the ``$CROSS_COMPILE`` environment variable to the prefix of the cross +tools and add the tools to ``$PATH``, :: + +$ export CROSS_COMPILE=riscv64-unknown-linux-gnu- +$ export PATH="$PREFIX/bin:$PATH" + +Also set ``$SYSROOT``, where all QEMU cross-compiled dependencies will be +installed. The toolchain installation likely created a 'sysroot' directory +at ``$PREFIX/sysroot``, which is the default location for most cross +tools, making it a good location, :: + + $ mkdir -p "$PREFIX/sysroot" + $ export SYSROOT="$PREFIX/sysroot" + +Create a pkg-config wrapper +^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The build processes of QEMU and some of its dependencies depend on +pkg-config. Create a wrapper script for it which works for the cross +environment: :: + + $ cat <<EOF >"$PREFIX/bin/${CROSS_COMPILE}pkg-config" + #!/bin/sh + + [ "\$SYSROOT" ] || exit 1 + + export PKG_CONFIG_PATH= + export PKG_CONFIG_LIBDIR="\${SYSROOT}/usr/lib/pkgconfig:\${SYSROOT}/usr/lib64/pkgconfig:\${SYSROOT}/usr/share/pkgconfig" + + exec pkg-config "\$@" + EOF + $ chmod +x "$PREFIX/bin/${CROSS_COMPILE}pkg-config" + +Create a cross-file for meson builds +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +meson setup, used by some of QEMU's dependencies, needs a "cross-file" to +configure the cross environment. Create one, :: + + $ cd "$WORK_DIR" + $ cat <<EOF >cross_file.txt + [host_machine] + system = 'linux' + cpu_family = 'riscv64' + cpu = 'riscv64' + endian = 'little' + + [binaries] + c = '${CROSS_COMPILE}gcc' + cpp = '${CROSS_COMPILE}g++' + ar = '${CROSS_COMPILE}ar' + ld = '${CROSS_COMPILE}ld' + objcopy = '${CROSS_COMPILE}objcopy' + strip = '${CROSS_COMPILE}strip' + pkgconfig = '${CROSS_COMPILE}pkg-config' + EOF + +Cross-compile dependencies +-------------------------- + +glibc +^^^^^ + +If [riscv-toolchain]_ was selected for the toolchain then this step is +already complete and glibc has already been installed into ``$SYSROOT``. +Otherwise, cross-compile glibc and install it to ``$SYSROOT``. + +libffi +^^^^^^ + +:: + + $ cd "$WORK_DIR" + $ git clone https://gitlab.freedesktop.org/gstreamer/meson-ports/libffi.git + $ cd libffi + $ meson setup --cross-file ../cross_file.txt --prefix="$SYSROOT/usr" _build + $ ninja -C _build + $ ninja -C _build install + +*Building libffi seperately avoids a compilation error generated when +building it as a subproject of glib.* + +glib +^^^^ + +:: + + $ cd "$WORK_DIR" + $ git clone https://github.com/GNOME/glib.git + $ cd glib + $ meson setup --cross-file ../cross_file.txt --prefix="$SYSROOT/usr" _build + $ ninja -C _build + $ ninja -C _build install + +libslirp [optional] +^^^^^^^^^^^^^^^^^^^ + +:: + + $ cd "$WORK_DIR" + $ git clone https://gitlab.com/qemu-project/libslirp.git + $ cd libslirp + $ meson setup --cross-file ../cross_file.txt --prefix="$SYSROOT/usr" _build + $ ninja -C _build + $ ninja -C _build install + +pixman +^^^^^^ + +First ensure the 'libtool' package is installed, e.g. +``sudo dnf install libtool`` or ``sudo apt install libtool`` + +:: + + $ cd "$WORK_DIR" + $ git clone https://gitlab.freedesktop.org/pixman/pixman + $ cd pixman + $ ./autogen.sh + $ ./configure --prefix="$SYSROOT/usr" --host=riscv64-unknown-linux-gnu + $ make -j$(nproc) + $ make install + +Cross-compile QEMU +------------------ + +:: + + $ cd "$WORK_DIR" + $ git clone https://gitlab.com/qemu-project/qemu.git + $ cd qemu + $ mkdir -p build/install_dir + $ cd build + $ ../configure --target-list=riscv64-softmmu --cross-prefix=$CROSS_COMPILE --prefix="$PWD/install_dir" + $ make -j$(nproc) + $ make install + +*Cross-compiling QEMU with different configurations may require more +dependencies to be built and installed in the sysroot.* + +Running QEMU +------------ + +``build/install_dir`` may now be copied to the target and its bin +directory may be added to the target user's PATH. Prior to running +QEMU, ensure all the libraries it depends on are present, :: + + $ ldd /path/to/bin/qemu-system-riscv64 + +For example, it may necessary to install zlib libraries, e.g. +``sudo dnf install zlib-devel`` or ``sudo apt install zlib1g-dev`` + +Subsequent QEMU Cross-compiling +------------------------------- + +Unless it's necessary to update and recompile the toolchain or +dependencies, then most steps do not need to be repeated for subsequent +compiles. Simply ensure the toolchain is in ``$PATH``, ``$SYSROOT`` points +at the sysroot, and then follow the QEMU cross-compile steps in +"Cross-compile QEMU". For example, :: + + $ export PATH="$HOME/opt/riscv/bin:$PATH" + $ export SYSROOT="$HOME/opt/riscv/sysroot" + $ cd /path/to/qemu + $ mkdir -p build/install_dir + $ cd build + $ ../configure --target-list=riscv64-softmmu --cross-prefix=riscv64-unknown-linux-gnu- --prefix="$PWD/install_dir" + $ make -j + $ make install + +References +---------- + +.. [riscv-toolchain] https://github.com/riscv/riscv-gnu-toolchain diff --git a/docs/devel/index-build.rst b/docs/devel/index-build.rst index 57e8d39d9856..d3c85927be24 100644 --- a/docs/devel/index-build.rst +++ b/docs/devel/index-build.rst @@ -9,6 +9,7 @@ the basics if you are adding new files and targets to the build. :maxdepth: 3 build-system + cross-compiling kconfig testing acpi-bits -- 2.41.0
