Andrew Jones <ajo...@ventanamicro.com> writes:
> 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. "some architectures" - most of the cross compile stuff is hidden away by the build system on systems with appropriate development libraries installed. I think we would be remiss if we didn't just outline the common case: ../configure --cross-prefix=riscv64-linux-gnu- I think we could make it clearer that in most cases you don't need to prepare and cross-compile a bunch of dependencies lest we send developers down a rabbit hole. Maybe build-system.rst be updated and this reference it for the common case? > 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 -- Alex Bennée Virtualisation Tech Lead @ Linaro
