add: readme

README.md

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+# KFS (Kernel From Scratch)
+
+This project aims to explore how a kernel works by building our own, gaining hands-on experience with core concepts like memory management, interrupt, keyboard driver, etc
+
+## INSTALLATION
+
+### Cross compile the compile
+[THE DOCUMENTATION](https://wiki.osdev.org/GCC_Cross-Compiler)
+- install requirement follow [THE DOCUMENTATION](https://wiki.osdev.org/GCC_Cross-Compiler)
+- Setup the shell
+``` sh
+export PREFIX="$HOME/opt/cross"
+export TARGET=i386-elf
+export PATH="$PREFIX/bin:$PATH"
+mkdir $HOME/src
+cd $HOME/src
+```
+- Download [binutils](https://ftp.gnu.org/gnu/binutils/?C=M;O=D)
+- Download [gcc](https://ftp.gnu.org/gnu/gcc/?C=M;O=D)
+- Download [gdb](https://ftp.gnu.org/gnu/gdb/?C=M;O=D)
+- extract archives
+``` sh
+tar xf [your binutils archive]
+tar xf [your gcc archive]
+tar xf [your gdb archive]
+```
+- (protips use -j [nb core])
+- Compile binutils
+``` sh
+cd $HOME/src
+mkdir build-binutils
+
+cd build-binutils
+../binutils-x.y.z/configure --target=$TARGET --prefix="$PREFIX" --with-sysroot --disable-nls --disable-werror
+make
+make install
+```
+- Compile gdb
+``` sh
+cd $HOME/src
+mkdir build-gdb
+
+cd build-gdb
+../gdb.x.y.z/configure --target=$TARGET --prefix="$PREFIX" --disable-werror
+make all-gdb
+make install-gdb
+make
+make install
+```
+- Compile gcc
+``` sh
+cd $HOME/src
+
+# 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
+make all-gcc
+make all-target-libgcc
+make install-gcc
+make install-target-libgcc
+```
+
+### Compile and the start the kernel
+``` sh
+make run
+```