stealthos

StealthOs is meant to be a study of operating systems, Beware I am not a very competent C or assembly developer. This code may contain bugs and errors and use at your own risk. If you do continue Please try it in a virtual machine.

building

The build process requires a cross compiler

Cross compilers

Cross compilers are compiler which can be used to compile code written in the host system to another system of same or different architecture, size, any attributes really.

I'll be storing my cross compiler in /usr/local/cross since im the administrator of my system.

prequisites

download the following for compiling a cross compiler.

• binutils release preferably the latest.
• gcc release preferably the latest

Its also helpful to have the following enviornment variables

export TARGET=x86_64 # specifing that our target platform is an x86_64 machine using the elf format
export PREFIX="/usr/local/cross" # where to install the cross compiler

Caution

DO NOT MINDLESSLY TYPE COMMANDS You may mess up your local gcc/libgcc these above variables get reset per shell thus it is import to confirm that these are properly set before typing commands

make a new directory somewhere inside your projects directory (if you have one)

mkdir cross
mkdir cross/build-binutils
mkdir cross/build-gcc

binutils

extract the release you got then cd into thebuild-binutils directory.

Next we must configure this source code to fit our job. thats via the configure executable inside this directory

../binutils.x.x.x/configure --target=$TARGET --prefix="$PREFIX" --with-sysroot --disable-nls --disable-werror

explanation of the above command

• target: the platform we are targeting
• prefix: where binutils is to be installed
• disable-werror: disables treating erros as warnings in the build
• with-sysroot: (help needed)
• diable-nls: stop using native language support

we must then compile and install to our prefix

make -j $(nproc)
make install

the -j$(nproc) just makes the compiler use all the available cores. i really didnt want to wait for this build

And there you have it you have bin utils up

GCC

similarily we will be compiling GCC. begin by switching to the gcc directory.

Then you'll have to create a file named t-x86_64-elf insideconfig/i386 make the directory if need be.

# Add libgcc multilib variant without red zone requirement

MULTILIB_OPTION += mno-red-zone
MULTILIB_DIRNAMES += no-red-zone

what we are doing here is disabling red zone. Which is explained very well in the os dev wiki

edit gcc/config.gcc

 x86_64-*-elf*)
	tmake_file="${tmake_file} i386/t-x86_64-elf" # include the new multilib configuration
	tm_file="${tm_file} i386/unix.h i386/att.h elfos.h newlib-stdint.h i386/i386elf.h i386/x86-64.h"
	;;

then build this;

# The $PREFIX/bin dir _must_ be in the PATH. We did that above.
which -- $TARGET-as || echo $TARGET-as is not in the PATH

mkdir build-gcc
cd build-gcc
../gcc-x.y.z/configure --target=$TARGET --prefix="$PREFIX" --disable-nls --enable-languages=c,c++ --without-headers --disable-hosted-libstdcxx
make all-gcc
make all-target-libgcc
make all-target-libstdc++-v3
make install-gcc
make install-target-libgcc
make install-target-libstdc++-v3

these commands were copied from the gcc cross compiler article of osdev.org

building the os

get the source code; git clone . edit the TC-stealthos.cmake toolchain file put the path of the cross compiler in there

mkdir build
cd build
cmake .. --DCMAKE_TOOLCHAIN_FILE=TC-stealthos.cmake
cmake --build . --target iso

and you'll have a stealthos.iso file

resources used

• the little os book
• OS dev wiki