Intro
-----

You can compile AbaOS from a 32-bit host or chroot (e.g. Arch32 chroot).
But you have to be extremly careful that nothing ceeps into the kernel
from the host system.

You can also create a cross-compilation environment. Now, we don't need
a full fledged chain, linker and C compiler is enough. AbaOs has a small
integrated C library which is sufficient to build the kernel.

gcc
---

mkdir -p $HOME/cross-compilers/gcc
cd $HOME/cross-compilers/gcc
wget https://ftp.gnu.org/gnu/binutils/binutils-2.28.tar.gz
tar xf binutils-2.28.tar.gz
mkdir binutils-build
cd binutils-build
../binutils-2.28/configure --target=i486-elf --prefix=$HOME/cross-compilers --disable-nls -v
make all
make check
make install
cd ..

wget https://gmplib.org/download/gmp/gmp-6.1.2.tar.lz
tar xf gmp-6.1.2.tar.lz
mkdir gmp-build
cd gmp-build
../gmp-6.1.2/configure --build=i486-elf --host=i486-elf --prefix=$HOME/cross-compilers
make all
make check
make install
cd ..

wget http://www.mpfr.org/mpfr-current/mpfr-3.1.5.tar.gz
tar xf mpfr-3.1.5.tar.gz
mkdir mpfr-build
cd mpfr-build
../mpfr-3.1.5/configure -build=i486-elf --host=i486-elf --prefix=$HOME/cross-compilers \
	--with-gmp=$HOME/cross-compilers
make all
make check
make install
cd ..

wget ftp://ftp.gnu.org/gnu/mpc/mpc-1.0.3.tar.gz
tar xf mpc-1.0.3.tar.gz
mkdir mpc-build
cd mpc-build
../mpc-1.0.3/configure --host=i486-elf --target=i486-elf \
	--prefix=$HOME/cross-compilers \
	--with-gmp=$HOME/cross-compilers \
	--with-mpfr=$HOME/cross-compilers
make all
make check
make install
cd ..

wget ftp://ftp.mpi-sb.mpg.de/pub/gnu/mirror/gcc.gnu.org/pub/gcc/releases/gcc-7.1.0/gcc-7.1.0.tar.gz
tar zxf gcc-7.1.0.tar.gz
mkdir gcc-build
cd gcc-build
../gcc-7.1.0/configure --target=i486-elf --prefix=$HOME/cross-compilers \
	--with-gnu-as --with-gnu-ld \
	--disable-nls --enable-languages=c --disable-libgcj --without-headers \
	--with-gmp=$HOME/cross-compilers \
	--with-mpfr=$HOME/cross-compilers \
	--with-mpc=$HOME/cross-compilers
make all-gcc
make all-target-libgcc
make install-gcc
make install-target-libgcc

Compile abaos and libc tests with:

setenv PATH "${PATH}:$HOME/cross-compilers"
make clean all CC=i486-elf-gcc LD=i486-elf-ld


tcc
---

mkdir -p $HOME/cross-compilers/tcc
cd $HOME/cross-compilers/tcc
wget https://ftp.gnu.org/gnu/binutils/binutils-2.28.tar.gz
tar xf binutils-2.28.tar.gz
mkdir binutils-build
cd binutils-build
../binutils-2.28/configure --target=i486-elf --prefix=$HOME/cross-compilers --disable-nls -v
make all
make check
make install
cd ..

mkdir -p $HOME/cross-compilers/tcc
cd $HOME/cross-compilers/tcc
git clone git://repo.or.cz/tinycc.git
cd tinycc
./configure --cpu=i386 --enable-cross --prefix=$HOME/cross-compilers
make
cd ..

Compile abaos and libc tests with:

setenv PATH "${PATH}:$HOME/cross-compilers"
make clean all CC=i386-tcc LD=i486-elf-ld

pcc
---

mkdir -p $HOME/cross-compilers/pcc
cd $HOME/cross-compilers/pcc
wget https://ftp.gnu.org/gnu/binutils/binutils-2.28.tar.gz
tar xf binutils-2.28.tar.gz
mkdir binutils-build
cd binutils-build
../binutils-2.28/configure --target=i486-unknown-linux-gnu --prefix=$HOME/cross-compilers --disable-nls -v
make all
make check
make install
cd ..

mkdir -p $HOME/cross-compilers/pcc
cvs -d :pserver:anonymous@pcc.ludd.ltu.se:/cvsroot co pcc-libs
mkdir pcc-libs-build
cd pcc-libs-build
../pcc-libs/configure --target=i486-unknown-linux-gnu --prefix=$HOME/cross-compilers
make
make install
cd ..

cvs -d :pserver:anonymous@pcc.ludd.ltu.se:/cvsroot co pcc
mkdir pcc-build
cd pcc-build
../pcc/configure --target=i486-unknown-linux-gnu --prefix=$HOME/cross-compilers
make
make install

Compile abaos and libc tests with:

setenv PATH "${PATH}:$HOME/cross-compilers"
make clean all CC=i486-unknown-linux-gnu-pcc LD=i486-unknown-linux-gnu-ld

clang
-----

Clang is easy, usually it already supports common targets. Just
for the kernel we need a i486 linker from binutils:

mkdir -p $HOME/cross-compilers/pcc
cd $HOME/cross-compilers/pcc
wget https://ftp.gnu.org/gnu/binutils/binutils-2.28.tar.gz
tar xf binutils-2.28.tar.gz
mkdir binutils-build
cd binutils-build
../binutils-2.28/configure --target=i486-unknown-linux-gnu --prefix=$HOME/cross-compilers --disable-nls -v
make all
make check
make install
cd ..

Compile abaos and libc tests with:

setenv PATH "${PATH}:$HOME/cross-compilers"
make clean all run-qemu CC='clang -target i386-pc-none-abi' LD=i486-unknown-linux-gnu-ld

Links
-----

https://ftp.gnu.org/gnu/binutils/
http://wiki.osdev.org/Target_Triplet
http://wiki.osdev.org/GCC_Cross-Compiler